--- DOAJ_listed: '1' OA_place: publisher OA_type: gold PlanS_conform: '1' _id: '21501' abstract: - lang: eng text: "Kinetically constrained models were originally introduced to capture slow relaxation in glassy systems, where dynamics are hindered by local constraints instead of energy barriers. Their quantum counterparts have recently drawn attention for exhibiting highly degenerate eigenstates at zero energy—known as zero modes—stemming from chiral symmetry. Yet, the structure and implications of these zero modes remain poorly understood. In this work, we focus on the properties of the zero mode subspace in quantum kinetically constrained models with a U(1) particle-conservation symmetry. We use the U(1) East, which lacks inversion symmetry, and the inversion-symmetric U(1) East-West models to illustrate our two main results. First, we observe that the simultaneous presence of constraints and chiral symmetry generally leads to a parametric increase in the number of zero modes due to the fragmentation of the many-body\r\nHilbert space into disconnected sectors. Second, we generalize the concept of compact localized states from single-particle physics and introduce the notion of collective bound states, a special kind of nonergodic eigenstates that are robust to enlarging the system size. We formulate sufficient criteria for their existence, arguing that the degenerate zero mode subspace plays a central role, and demonstrate bound states in both example models and in a two-dimensional model, the U(1) North-East, and in the pairflip model, a system without particle conservation. Our results motivate a systematic study of bound states and their relation to ergodicity breaking, transport, and other properties of quantum kinetically constrained\r\nmodels. " acknowledgement: The authors acknowledge useful discussions with Berislav Buca. This work was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 850899). M.L. acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy—EXC-2111—390814868. This research was supported in part by grant NSF PHY-2309135 to the Kavli Institute for Theoretical Physics (KITP). article_number: '010352' article_processing_charge: Yes article_type: original arxiv: 1 author: - first_name: Eulalia full_name: Nicolau Jimenez, Eulalia id: 04b4791c-8fd7-11ee-a7df-be2fdc569c48 last_name: Nicolau Jimenez - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: Nicolau Jimenez E, Ljubotina M, Serbyn M. Fragmentation, zero modes, and collective bound states in constrained models. PRX Quantum. 2026;7. doi:10.1103/sl79-1xgb apa: Nicolau Jimenez, E., Ljubotina, M., & Serbyn, M. (2026). Fragmentation, zero modes, and collective bound states in constrained models. PRX Quantum. American Physical Society. https://doi.org/10.1103/sl79-1xgb chicago: Nicolau Jimenez, Eulalia, Marko Ljubotina, and Maksym Serbyn. “Fragmentation, Zero Modes, and Collective Bound States in Constrained Models.” PRX Quantum. American Physical Society, 2026. https://doi.org/10.1103/sl79-1xgb. ieee: E. Nicolau Jimenez, M. Ljubotina, and M. Serbyn, “Fragmentation, zero modes, and collective bound states in constrained models,” PRX Quantum, vol. 7. American Physical Society, 2026. ista: Nicolau Jimenez E, Ljubotina M, Serbyn M. 2026. Fragmentation, zero modes, and collective bound states in constrained models. PRX Quantum. 7, 010352. mla: Nicolau Jimenez, Eulalia, et al. “Fragmentation, Zero Modes, and Collective Bound States in Constrained Models.” PRX Quantum, vol. 7, 010352, American Physical Society, 2026, doi:10.1103/sl79-1xgb. short: E. Nicolau Jimenez, M. Ljubotina, M. Serbyn, PRX Quantum 7 (2026). corr_author: '1' date_created: 2026-03-28T14:57:56Z date_published: 2026-03-13T00:00:00Z date_updated: 2026-03-30T06:09:28Z day: '13' ddc: - '530' department: - _id: MaSe doi: 10.1103/sl79-1xgb ec_funded: 1 external_id: arxiv: - '2504.17627' file: - access_level: open_access checksum: d155ffa9e1a8275702149165f4bf963c content_type: application/pdf creator: dernst date_created: 2026-03-30T06:08:07Z date_updated: 2026-03-30T06:08:07Z file_id: '21505' file_name: 2026_PRXQuantum_Nicolau.pdf file_size: 1848724 relation: main_file success: 1 file_date_updated: 2026-03-30T06:08:07Z has_accepted_license: '1' intvolume: ' 7' language: - iso: eng month: '03' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: PRX Quantum publication_identifier: eissn: - 2691-3399 publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Fragmentation, zero modes, and collective bound states in constrained models tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 7 year: '2026' ... --- DOAJ_listed: '1' OA_place: publisher OA_type: gold PlanS_conform: '1' _id: '21917' abstract: - lang: eng text: A defining feature of quantum many-body systems is the exponential scaling of the Hilbert space with the number of degrees of freedom. This exponential complexity naïvely renders a complete state characterization, for instance via the complete set of bipartite Renyi entropies for all disjoint regions, a challenging task. Recently, a compact way of storing subregions' purities by encoding them as amplitudes of a fictitious quantum wave function, known as entanglement feature, was proposed. Notably, the entanglement feature can be a simple object even for highly entangled quantum states. However the complexity and practical usage of the entanglement feature for general quantum states has not been explored. In this work, we demonstrate that the entanglement feature can be efficiently learned using only a polynomial amount of samples in the number of degrees of freedom through the so-called tensor cross interpolation (TCI) algorithm, assuming it is expressible as a finite bond dimension MPS. We benchmark this learning process on Haar and random MPS states, confirming analytic expectations. Applying the TCI algorithm to quantum eigenstates of various one dimensional quantum systems, we identify cases where eigenstates have entanglement feature learnable with TCI. We conclude with possible applications of the learned entanglement feature, such as quantifying the distance between different entanglement patterns and finding the optimal one-dimensional ordering of physical indices in a given state, highlighting the potential utility of the proposed purity interpolation method. acknowledgement: "We acknowledge useful discussions with Richard Küng\r\non the interpolation methods and error spreading, Ilia\r\nA. Luchnikov, Margarita Davydova, and, in particular, Hiroshi Shinaoka, Marc Ritter, Yuriel Nuñez\r\nfor useful discussions about TCI and the various\r\nworkarounds within the TensorCrossInterpolation.jl\r\nlibrary. We also acknowledge the comments of anonymous Referee B, that encouraged us to expand the\r\nmanuscript with discussion of additional applications\r\nof entanglement feature in Section 4.3. M.S. acknowledges discussions with D. V. Savostyanov at the 2nd\r\nInternational Quantum Tensor Networks (IQTN) plenary meeting at Flatiron Institute’s Center for Computational Quantum Physics (CCQ) for introduction\r\nto the TCI approach. D.K and M.S. acknowledge support by the European Research Council (ERC) under We acknowledge useful discussions with Richard Küng\r\non the interpolation methods and error spreading, Ilia\r\nA. Luchnikov, Margarita Davydova, and, in particular, Hiroshi Shinaoka, Marc Ritter, Yuriel Nuñez\r\nfor useful discussions about TCI and the various\r\nworkarounds within the TensorCrossInterpolation.jl\r\nlibrary. We also acknowledge the comments of anonymous Referee B, that encouraged us to expand the\r\nmanuscript with discussion of additional applications\r\nof entanglement feature in Section 4.3. M.S. acknowledges discussions with D. V. Savostyanov at the 2nd\r\nInternational Quantum Tensor Networks (IQTN) plenary meeting at Flatiron Institute’s Center for Computational Quantum Physics (CCQ) for introduction\r\nto the TCI approach. D.K and M.S. acknowledge support by the European Research Council (ERC) under We acknowledge useful discussions with Richard Küng\r\non the interpolation methods and error spreading, Ilia\r\nA. Luchnikov, Margarita Davydova, and, in particular, Hiroshi Shinaoka, Marc Ritter, Yuriel Nuñez\r\nfor useful discussions about TCI and the various\r\nworkarounds within the TensorCrossInterpolation.jl\r\nlibrary. We also acknowledge the comments of anonymous Referee B, that encouraged us to expand the\r\nmanuscript with discussion of additional applications\r\nof entanglement feature in Section 4.3. M.S. acknowledges discussions with D. V. Savostyanov at the 2nd\r\nInternational Quantum Tensor Networks (IQTN) plenary meeting at Flatiron Institute’s Center for Computational Quantum Physics (CCQ) for introduction\r\nto the TCI approach. D.K and M.S. acknowledge support by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 850899).\r\nR.V. acknowledges partial support from the US Department of Energy, Office of Science, Basic Energy\r\nSciences, under award No. DE-SC0023999, and the\r\nSwiss National Science Foundation (grant 10008234).\r\nThis research was supported in part by grant NSF\r\nPHY-2309135 to the Kavli Institute for Theoretical\r\nPhysics (KITP)" article_number: '2114' article_processing_charge: Yes article_type: original arxiv: 1 author: - first_name: Dmytro full_name: Kolisnyk, Dmytro id: 530a7320-5355-11ee-ae5a-82a46997aaa7 last_name: Kolisnyk orcid: 0000-0002-8612-8202 - first_name: Raimel A full_name: Medina Ramos, Raimel A id: CE680B90-D85A-11E9-B684-C920E6697425 last_name: Medina Ramos orcid: 0000-0002-5383-2869 - first_name: Romain full_name: Vasseur, Romain last_name: Vasseur - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: Kolisnyk D, Medina Ramos RA, Vasseur R, Serbyn M. Tensor cross interpolation of purities in quantum many-body systems. Quantum. 2026;10. doi:10.22331/q-2026-05-22-2114 apa: Kolisnyk, D., Medina Ramos, R. A., Vasseur, R., & Serbyn, M. (2026). Tensor cross interpolation of purities in quantum many-body systems. Quantum. Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften. https://doi.org/10.22331/q-2026-05-22-2114 chicago: Kolisnyk, Dmytro, Raimel A Medina Ramos, Romain Vasseur, and Maksym Serbyn. “Tensor Cross Interpolation of Purities in Quantum Many-Body Systems.” Quantum. Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften, 2026. https://doi.org/10.22331/q-2026-05-22-2114. ieee: D. Kolisnyk, R. A. Medina Ramos, R. Vasseur, and M. Serbyn, “Tensor cross interpolation of purities in quantum many-body systems,” Quantum, vol. 10. Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften, 2026. ista: Kolisnyk D, Medina Ramos RA, Vasseur R, Serbyn M. 2026. Tensor cross interpolation of purities in quantum many-body systems. Quantum. 10, 2114. mla: Kolisnyk, Dmytro, et al. “Tensor Cross Interpolation of Purities in Quantum Many-Body Systems.” Quantum, vol. 10, 2114, Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften, 2026, doi:10.22331/q-2026-05-22-2114. short: D. Kolisnyk, R.A. Medina Ramos, R. Vasseur, M. Serbyn, Quantum 10 (2026). corr_author: '1' date_created: 2026-05-26T19:39:12Z date_published: 2026-05-22T00:00:00Z date_updated: 2026-06-02T09:15:13Z day: '22' ddc: - '530' department: - _id: MaSe - _id: GradSch doi: 10.22331/q-2026-05-22-2114 ec_funded: 1 external_id: arxiv: - '2503.17230' file: - access_level: open_access checksum: f8ce78607ad06120cdf894dc8cef55da content_type: application/pdf creator: dernst date_created: 2026-06-02T09:12:11Z date_updated: 2026-06-02T09:12:11Z file_id: '21939' file_name: 2026_Quantum_Kolisnyk.pdf file_size: 3284798 relation: main_file success: 1 file_date_updated: 2026-06-02T09:12:11Z has_accepted_license: '1' intvolume: ' 10' language: - iso: eng month: '05' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: Quantum publication_identifier: eissn: - 2521-327X publication_status: published publisher: Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften quality_controlled: '1' status: public title: Tensor cross interpolation of purities in quantum many-body systems tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 10 year: '2026' ... --- _id: '19623' abstract: - lang: eng text: "Persistent revivals recently observed in Rydberg atom simulators have challenged our understanding of thermalization and attracted much interest to the concept of quantum many-body scars (QMBSs). QMBSs are non-thermal highly excited eigenstates that coexist with typical eigenstates in the spectrum of many-body Hamiltonians, and have since been reported in multiple theoretical models, including the so-called PXP model, approximately realized by Rydberg simulators. At the same time, questions of how common QMBSs are and in what models they are physically realized remain open. In this Letter, we demonstrate that QMBSs exist in a broader family of models that includes and generalizes PXP to longer-range constraints and states with different periodicity. We show that in each model, multiple QMBS families can be found. Each of them relies on a different approximate \U0001D530\U0001D532⁡(2) algebra, leading to oscillatory dynamics in all cases. However, in contrast to the PXP model, their observation requires launching dynamics from weakly entangled initial states rather than from a product state. QMBSs reported here may be experimentally probed using Rydberg atom simulator in the regime of longer-range Rydberg blockades." acknowledged_ssus: - _id: ScienComp acknowledgement: The authors are grateful to Zlatko Papić, Dolev Bluvstein, Nishad Maskara, Marcello Dalmonte, Thomas Iadecola, and Johannes Feldmeier for insightful discussions. A. K., M. L., and M. S. acknowledge support by the European Research Council under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 850899). J.-Y. D. acknowledges funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 101034413. article_processing_charge: No author: - first_name: Jean-Yves Marc full_name: Desaules, Jean-Yves Marc id: 6c292945-a610-11ed-9eec-c3be1ad62a80 last_name: Desaules orcid: 0000-0002-3749-6375 citation: ama: Desaules J-YM. Research Data for “Quantum Many-Body Scars beyond the PXP Model in Rydberg Simulators.” 2025. doi:10.15479/AT:ISTA:19623 apa: Desaules, J.-Y. M. (2025). Research Data for “Quantum Many-Body Scars beyond the PXP Model in Rydberg Simulators.” Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:19623 chicago: Desaules, Jean-Yves Marc. “Research Data for ‘Quantum Many-Body Scars beyond the PXP Model in Rydberg Simulators.’” Institute of Science and Technology Austria, 2025. https://doi.org/10.15479/AT:ISTA:19623. ieee: J.-Y. M. Desaules, “Research Data for ‘Quantum Many-Body Scars beyond the PXP Model in Rydberg Simulators.’” Institute of Science and Technology Austria, 2025. ista: Desaules J-YM. 2025. Research Data for ‘Quantum Many-Body Scars beyond the PXP Model in Rydberg Simulators’, Institute of Science and Technology Austria, 10.15479/AT:ISTA:19623. mla: Desaules, Jean-Yves Marc. Research Data for “Quantum Many-Body Scars beyond the PXP Model in Rydberg Simulators.” Institute of Science and Technology Austria, 2025, doi:10.15479/AT:ISTA:19623. short: J.-Y.M. Desaules, (2025). contributor: - contributor_type: researcher first_name: Aron id: ade85a9c-3200-11ee-973b-91c1eb240410 last_name: Kerschbaumer - contributor_type: researcher first_name: Marko last_name: Ljubotina - contributor_type: researcher first_name: Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 - contributor_type: researcher first_name: Jean-Yves Marc id: 6c292945-a610-11ed-9eec-c3be1ad62a80 last_name: Desaules orcid: 0000-0002-3749-6375 corr_author: '1' date_created: 2025-04-24T19:58:46Z date_published: 2025-04-24T00:00:00Z date_updated: 2026-06-10T08:40:52Z day: '24' ddc: - '530' department: - _id: MaSe doi: 10.15479/AT:ISTA:19623 ec_funded: 1 file: - access_level: open_access checksum: d073314c4dc95d93feaadbff188ce4a1 content_type: application/zip creator: jdesaule date_created: 2025-05-05T07:14:17Z date_updated: 2025-05-05T07:14:17Z file_id: '19646' file_name: Data+Code.zip file_size: 583478621 relation: main_file success: 1 - access_level: open_access checksum: d386a2364fb1147ef6dad30ad029c080 content_type: text/plain creator: jdesaule date_created: 2025-05-05T07:13:46Z date_updated: 2025-05-05T07:13:46Z file_id: '19647' file_name: readme.txt file_size: 15856 relation: main_file success: 1 file_date_updated: 2025-05-05T07:14:17Z has_accepted_license: '1' keyword: - quantum many-body scars - non-equilibrium physics - Rydberg atoms license: https://creativecommons.org/licenses/by-nc/4.0/ month: '04' oa: 1 oa_version: Published Version project: - _id: fc2ed2f7-9c52-11eb-aca3-c01059dda49c call_identifier: H2020 grant_number: '101034413' name: 'IST-BRIDGE: International postdoctoral program' - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publisher: Institute of Science and Technology Austria related_material: record: - id: '19664' relation: used_in_publication status: public status: public title: Research Data for "Quantum Many-Body Scars beyond the PXP Model in Rydberg Simulators" tmp: image: /images/cc_by_nc.png legal_code_url: https://creativecommons.org/licenses/by-nc/4.0/legalcode name: Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) short: CC BY-NC (4.0) type: research_data user_id: 68b8ca59-c5b3-11ee-8790-cd641c68093d year: '2025' ... --- OA_place: publisher OA_type: hybrid _id: '19664' abstract: - lang: eng text: Persistent revivals recently observed in Rydberg atom simulators have challenged our understanding of thermalization and attracted much interest to the concept of quantum many-body scars (QMBSs). QMBSs are non-thermal highly excited eigenstates that coexist with typical eigenstates in the spectrum of many-body Hamiltonians, and have since been reported in multiple theoretical models, including the so-called PXP model, approximately realized by Rydberg simulators. At the same time, questions of how common QMBSs are and in what models they are physically realized remain open. In this Letter, we demonstrate that QMBSs exist in a broader family of models that includes and generalizes PXP to longer-range constraints and states with different periodicity. We show that in each model, multiple QMBS families can be found. Each of them relies on a different approximate algebra, leading to oscillatory dynamics in all cases. However, in contrast to the PXP model, their observation requires launching dynamics from weakly entangled initial states rather than from a product state. QMBSs reported here may be experimentally probed using Rydberg atom simulator in the regime of longer-range Rydberg blockades. acknowledgement: The authors are grateful to Zlatko Papić, Dolev Bluvstein, Nishad Maskara, Marcello Dalmonte, Thomas Iadecola, and Johannes Feldmeier for insightful discussions. A. K., M. L., and M. S. acknowledge support by the European Research Council under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 850899). J.-Y. D. acknowledges funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 101034413. article_number: '160401' article_processing_charge: Yes (via OA deal) article_type: original arxiv: 1 author: - first_name: Aron full_name: Kerschbaumer, Aron id: ade85a9c-3200-11ee-973b-91c1eb240410 last_name: Kerschbaumer orcid: 0009-0002-2370-8661 - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 - first_name: Jean-Yves Marc full_name: Desaules, Jean-Yves Marc id: 6c292945-a610-11ed-9eec-c3be1ad62a80 last_name: Desaules orcid: 0000-0002-3749-6375 citation: ama: Kerschbaumer A, Ljubotina M, Serbyn M, Desaules J-YM. Quantum many-body scars beyond the PXP model in Rydberg simulators. Physical Review Letters. 2025;134(16). doi:10.1103/PhysRevLett.134.160401 apa: Kerschbaumer, A., Ljubotina, M., Serbyn, M., & Desaules, J.-Y. M. (2025). Quantum many-body scars beyond the PXP model in Rydberg simulators. Physical Review Letters. American Physical Society. https://doi.org/10.1103/PhysRevLett.134.160401 chicago: Kerschbaumer, Aron, Marko Ljubotina, Maksym Serbyn, and Jean-Yves Marc Desaules. “Quantum Many-Body Scars beyond the PXP Model in Rydberg Simulators.” Physical Review Letters. American Physical Society, 2025. https://doi.org/10.1103/PhysRevLett.134.160401. ieee: A. Kerschbaumer, M. Ljubotina, M. Serbyn, and J.-Y. M. Desaules, “Quantum many-body scars beyond the PXP model in Rydberg simulators,” Physical Review Letters, vol. 134, no. 16. American Physical Society, 2025. ista: Kerschbaumer A, Ljubotina M, Serbyn M, Desaules J-YM. 2025. Quantum many-body scars beyond the PXP model in Rydberg simulators. Physical Review Letters. 134(16), 160401. mla: Kerschbaumer, Aron, et al. “Quantum Many-Body Scars beyond the PXP Model in Rydberg Simulators.” Physical Review Letters, vol. 134, no. 16, 160401, American Physical Society, 2025, doi:10.1103/PhysRevLett.134.160401. short: A. Kerschbaumer, M. Ljubotina, M. Serbyn, J.-Y.M. Desaules, Physical Review Letters 134 (2025). date_created: 2025-05-11T22:02:38Z date_published: 2025-04-22T00:00:00Z date_updated: 2026-06-10T08:40:51Z day: '22' ddc: - '530' department: - _id: MaSe doi: 10.1103/PhysRevLett.134.160401 ec_funded: 1 external_id: arxiv: - '2410.18913' isi: - '001480669300011' pmid: - '40344113' file: - access_level: open_access checksum: b7f581291e20f152d0efc64727314ca2 content_type: application/pdf creator: dernst date_created: 2025-05-12T07:33:38Z date_updated: 2025-05-12T07:33:38Z file_id: '19677' file_name: 2025_PhysReviewLetters_Kerschbaumer.pdf file_size: 1028993 relation: main_file success: 1 file_date_updated: 2025-05-12T07:33:38Z has_accepted_license: '1' intvolume: ' 134' isi: 1 issue: '16' language: - iso: eng month: '04' oa: 1 oa_version: Published Version pmid: 1 project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' - _id: fc2ed2f7-9c52-11eb-aca3-c01059dda49c call_identifier: H2020 grant_number: '101034413' name: 'IST-BRIDGE: International postdoctoral program' publication: Physical Review Letters publication_identifier: eissn: - 1079-7114 issn: - 0031-9007 publication_status: published publisher: American Physical Society quality_controlled: '1' related_material: link: - description: News on ISTA website relation: press_release url: https://ista.ac.at/en/news/a-sky-full-of-quantum-scars/ record: - id: '19623' relation: research_data status: public scopus_import: '1' status: public title: Quantum many-body scars beyond the PXP model in Rydberg simulators tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: ba8df636-2132-11f1-aed0-ed93e2281fdd volume: 134 year: '2025' ... --- OA_place: publisher OA_type: hybrid _id: '19833' abstract: - lang: eng text: Eigenstates of quantum many-body systems are often used to define phases of matter in and out of equilibrium; however, experimentally accessing highly excited eigenstates is a challenging task, calling for alternative strategies to dynamically probe nonequilibrium phases. In this work, we characterize the dynamical properties of a disordered spin chain, focusing on the spin-glass regime. Using tensor-network simulations, we observe oscillatory behavior of local expectation values and bipartite entanglement entropy. We explain these oscillations deep in the many-body localized spin-glass regime via a simple theoretical model. From perturbation theory, we predict the timescales up to which our analytical description is valid and confirm it with numerical simulations. Finally, we study the correlation length dynamics, which, after a long-time plateau, resume growing in line with renormalization group (RG) expectations. Our work suggests that RG predictions can be quantitatively tested against numerical simulations and experiments, potentially enabling microscopic descriptions of dynamical phases in large systems. acknowledgement: We thank D. A. Abanin for insightful discussions in the early stages of this work. P.B. acknowledges support by the Austrian Science Fund (FWF) [Grant Agreement No. 10.55776/ESP9057324]. This research was funded in whole or in part by the Austrian Science Fund (FWF) [10.55776/COE1]. The authors acknowledge support by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Grant Agreement No. 850899). M.L. acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy–EXC-2111–390814868. The authors acknowledge PRACE for awarding access to Joliot-Curie at GENCI@CEA, France, where the TEBD simulations were performed. The TEBD simulations were performed using the ITensor library [52]. article_number: L220202 article_processing_charge: Yes (in subscription journal) article_type: letter_note arxiv: 1 author: - first_name: Pietro full_name: Brighi, Pietro id: 4115AF5C-F248-11E8-B48F-1D18A9856A87 last_name: Brighi orcid: 0000-0002-7969-2729 - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: Brighi P, Ljubotina M, Serbyn M. Probing the many-body localized spin-glass phase through quench dynamics. Physical Review B. 2025;111(22). doi:10.1103/9fms-ygfz apa: Brighi, P., Ljubotina, M., & Serbyn, M. (2025). Probing the many-body localized spin-glass phase through quench dynamics. Physical Review B. American Physical Society. https://doi.org/10.1103/9fms-ygfz chicago: Brighi, Pietro, Marko Ljubotina, and Maksym Serbyn. “Probing the Many-Body Localized Spin-Glass Phase through Quench Dynamics.” Physical Review B. American Physical Society, 2025. https://doi.org/10.1103/9fms-ygfz. ieee: P. Brighi, M. Ljubotina, and M. Serbyn, “Probing the many-body localized spin-glass phase through quench dynamics,” Physical Review B, vol. 111, no. 22. American Physical Society, 2025. ista: Brighi P, Ljubotina M, Serbyn M. 2025. Probing the many-body localized spin-glass phase through quench dynamics. Physical Review B. 111(22), L220202. mla: Brighi, Pietro, et al. “Probing the Many-Body Localized Spin-Glass Phase through Quench Dynamics.” Physical Review B, vol. 111, no. 22, L220202, American Physical Society, 2025, doi:10.1103/9fms-ygfz. short: P. Brighi, M. Ljubotina, M. Serbyn, Physical Review B 111 (2025). date_created: 2025-06-13T06:09:38Z date_published: 2025-06-12T00:00:00Z date_updated: 2025-09-30T12:48:10Z day: '12' ddc: - '530' department: - _id: MaSe doi: 10.1103/9fms-ygfz ec_funded: 1 external_id: arxiv: - '2502.08192' isi: - '001511503800006' file: - access_level: open_access checksum: 7941f92124793a383ca132eee2c289c5 content_type: application/pdf creator: dernst date_created: 2025-06-23T06:28:17Z date_updated: 2025-06-23T06:28:17Z file_id: '19861' file_name: 2025_PhysReviewB_Brighi.pdf file_size: 1082749 relation: main_file success: 1 file_date_updated: 2025-06-23T06:28:17Z has_accepted_license: '1' intvolume: ' 111' isi: 1 issue: '22' language: - iso: eng month: '06' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: Physical Review B publication_identifier: eissn: - 2469-9969 issn: - 2469-9950 publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Probing the many-body localized spin-glass phase through quench dynamics tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 317138e5-6ab7-11ef-aa6d-ffef3953e345 volume: 111 year: '2025' ... --- APC_amount: 3599,50 EUR DOAJ_listed: '1' OA_place: publisher OA_type: gold PlanS_conform: '1' _id: '20646' abstract: - lang: eng text: Describing general quantum many-body dynamics is a challenging task due to the exponential growth of the Hilbert space with system size. The time-dependent variational principle (TDVP) provides a powerful tool to tackle this task by projecting quantum evolution onto a classical dynamical system within a variational manifold. In classical systems, periodic orbits play a crucial role in understanding the structure of the phase space and the long-term behavior of the system. However, finding periodic orbits is generally difficult, and their existence and properties in generic TDVP dynamics over matrix product states have remained largely unexplored. In this work, we develop an algorithm to systematically identify and characterize periodic orbits in TDVP dynamics. Applying our method to the periodically kicked Ising model, we uncover both stable and unstable periodic orbits. We characterize the Kolmogorov-Arnold-Moser tori in the vicinity of stable periodic orbits and track the change of the periodic orbits as we modify the Hamiltonian parameters. We observe that periodic orbits exist at any value of the coupling constant of the kicked Ising model between prethermal and fully thermalizing regimes, but their relevance to quantum dynamics and imprint on quantum eigenstates diminishes as the system leaves the prethermal regime. Our results demonstrate that periodic orbits provide valuable insights into the TDVP approximation of quantum many-body evolution and establish a closer connection between quantum and classical chaos. acknowledgement: We acknowledge useful discussions with C. Kollath, A. Green, and D. Huse. E.P., M.L., and M.S. acknowledge support by the European Research Council under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 850899). This research was funded in whole or in part by the Austrian Science Fund (FWF) (Grant No. 10.55776/COE1). For open access purposes, the author has applied a CC BY public copyright license to any author accepted manuscript version arising from this submission. M.L. acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy—EXC-2111—390814868. This research was supported in part by National Science Foundation (NSF) Grant No. PHY-2309135 to the Kavli Institute for Theoretical Physics (KITP) and by the Erwin Schrödinger International Institute for Mathematics and Physics (ESI). article_number: '040333' article_processing_charge: Yes article_type: original arxiv: 1 author: - first_name: Elena full_name: Petrova, Elena id: 0ac84990-897b-11ed-a09c-f5abb56a4ede last_name: Petrova - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 - first_name: Gökhan full_name: Yalniz, Gökhan id: 66E74FA2-D8BF-11E9-8249-8DE2E5697425 last_name: Yalniz orcid: 0000-0002-8490-9312 - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: Petrova E, Ljubotina M, Yalniz G, Serbyn M. Finding periodic orbits in projected quantum many-body dynamics. PRX Quantum. 2025;6(4). doi:10.1103/tldp-kvkd apa: Petrova, E., Ljubotina, M., Yalniz, G., & Serbyn, M. (2025). Finding periodic orbits in projected quantum many-body dynamics. PRX Quantum. American Physical Society. https://doi.org/10.1103/tldp-kvkd chicago: Petrova, Elena, Marko Ljubotina, Gökhan Yalniz, and Maksym Serbyn. “Finding Periodic Orbits in Projected Quantum Many-Body Dynamics.” PRX Quantum. American Physical Society, 2025. https://doi.org/10.1103/tldp-kvkd. ieee: E. Petrova, M. Ljubotina, G. Yalniz, and M. Serbyn, “Finding periodic orbits in projected quantum many-body dynamics,” PRX Quantum, vol. 6, no. 4. American Physical Society, 2025. ista: Petrova E, Ljubotina M, Yalniz G, Serbyn M. 2025. Finding periodic orbits in projected quantum many-body dynamics. PRX Quantum. 6(4), 040333. mla: Petrova, Elena, et al. “Finding Periodic Orbits in Projected Quantum Many-Body Dynamics.” PRX Quantum, vol. 6, no. 4, 040333, American Physical Society, 2025, doi:10.1103/tldp-kvkd. short: E. Petrova, M. Ljubotina, G. Yalniz, M. Serbyn, PRX Quantum 6 (2025). corr_author: '1' date_created: 2025-11-14T09:40:52Z date_published: 2025-11-12T00:00:00Z date_updated: 2026-05-20T07:59:04Z day: '12' ddc: - '539' department: - _id: GradSch - _id: BjHo - _id: MaSe doi: 10.1103/tldp-kvkd ec_funded: 1 external_id: arxiv: - '2504.12472' isi: - '001616473700003' file: - access_level: open_access checksum: 5d6d04ac518b4118405334e1ddc7a56d content_type: application/pdf creator: gyalniz date_created: 2025-11-14T09:44:10Z date_updated: 2025-11-14T09:44:10Z file_id: '20647' file_name: tldp-kvkd.pdf file_size: 2504713 relation: main_file success: 1 file_date_updated: 2025-11-14T09:44:10Z has_accepted_license: '1' intvolume: ' 6' isi: 1 issue: '4' language: - iso: eng month: '11' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' - _id: 3AC91DDA-15DF-11EA-824D-93A3E7B544D1 call_identifier: FWF name: FWF Open Access Fund publication: PRX Quantum publication_identifier: eissn: - 2691-3399 publication_status: published publisher: American Physical Society quality_controlled: '1' related_material: link: - description: News on ISTA website relation: press_release url: https://ista.ac.at/en/news/reaching-for-the-quantum-scars/ scopus_import: '1' status: public title: Finding periodic orbits in projected quantum many-body dynamics tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 6 year: '2025' ... --- APC_amount: 3711,01 EUR DOAJ_listed: '1' OA_place: publisher OA_type: gold _id: '18488' abstract: - lang: eng text: The advancement of quantum simulators motivates the development of a theoretical framework to assist with efficient state preparation in quantum many-body systems. Generally, preparing a target entangled state via unitary evolution with time-dependent couplings is a challenging task and very little is known about the existence of solutions and their properties. In this work we develop a constructive approach for preparing matrix product states (MPS) via continuous unitary evolution. We provide an explicit construction of the operator that exactly implements the evolution of a given MPS along a specified direction in its tangent space. This operator can be written as a sum of local terms of finite range, yet it is in general non-Hermitian. Relying on the explicit construction of the non-Hermitian generator of the dynamics, we demonstrate the existence of a Hermitian sequence of operators that implements the desired MPS evolution with an error that decreases exponentially with the operator range. The construction is benchmarked on an explicit periodic trajectory in a translationally invariant MPS manifold. We demonstrate that the Floquet unitary generating the dynamics over one period of the trajectory features an approximate MPS-like eigenstate embedded among a sea of thermalizing eigenstates. These results show that our construction is not only useful for state preparation and control of many-body systems, but also provides a generic route towards Floquet scars—periodically driven models with quasilocal generators of dynamics that have exact MPS eigenstates in their spectrum. acknowledgement: We thank L. Piroli, S. Garratt, and A. Molnár for insightful discussions. This research was funded in part by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreements No. 850899 and No. 863476), the Austrian Science Fund (FWF) (Grant DOIs 10.55776/COE1, 10.55776/P36305, and 10.55776/F71), and the European Union (NextGenerationEU). This work was performed in part at the Aspen Center for Physics, which is supported by National Science Foundation Grant PHY-2210452. This research was supported in part by NSF Grant PHY-2309135 to the Kavli Institute for Theoretical Physics (KITP). article_number: '040311' article_processing_charge: Yes article_type: original arxiv: 1 author: - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 - first_name: Elena full_name: Petrova, Elena id: 0ac84990-897b-11ed-a09c-f5abb56a4ede last_name: Petrova - first_name: Norbert full_name: Schuch, Norbert last_name: Schuch - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: Ljubotina M, Petrova E, Schuch N, Serbyn M. Tangent space generators of matrix product states and exact floquet quantum scars. PRX Quantum. 2024;5(4). doi:10.1103/prxquantum.5.040311 apa: Ljubotina, M., Petrova, E., Schuch, N., & Serbyn, M. (2024). Tangent space generators of matrix product states and exact floquet quantum scars. PRX Quantum. American Physical Society. https://doi.org/10.1103/prxquantum.5.040311 chicago: Ljubotina, Marko, Elena Petrova, Norbert Schuch, and Maksym Serbyn. “Tangent Space Generators of Matrix Product States and Exact Floquet Quantum Scars.” PRX Quantum. American Physical Society, 2024. https://doi.org/10.1103/prxquantum.5.040311. ieee: M. Ljubotina, E. Petrova, N. Schuch, and M. Serbyn, “Tangent space generators of matrix product states and exact floquet quantum scars,” PRX Quantum, vol. 5, no. 4. American Physical Society, 2024. ista: Ljubotina M, Petrova E, Schuch N, Serbyn M. 2024. Tangent space generators of matrix product states and exact floquet quantum scars. PRX Quantum. 5(4), 040311. mla: Ljubotina, Marko, et al. “Tangent Space Generators of Matrix Product States and Exact Floquet Quantum Scars.” PRX Quantum, vol. 5, no. 4, 040311, American Physical Society, 2024, doi:10.1103/prxquantum.5.040311. short: M. Ljubotina, E. Petrova, N. Schuch, M. Serbyn, PRX Quantum 5 (2024). corr_author: '1' date_created: 2024-10-29T16:04:05Z date_published: 2024-10-23T00:00:00Z date_updated: 2025-09-08T14:26:29Z day: '23' ddc: - '530' department: - _id: MaSe doi: 10.1103/prxquantum.5.040311 ec_funded: 1 external_id: arxiv: - '2403.12325' isi: - '001346198800001' file: - access_level: open_access checksum: 2e057ba021744d0a74602517935326b3 content_type: application/pdf creator: dernst date_created: 2024-10-30T08:59:09Z date_updated: 2024-10-30T08:59:09Z file_id: '18489' file_name: 2024_PRXQuantum_Ljubotina.pdf file_size: 1151431 relation: main_file success: 1 file_date_updated: 2024-10-30T08:59:09Z has_accepted_license: '1' intvolume: ' 5' isi: 1 issue: '4' language: - iso: eng month: '10' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: PRX Quantum publication_identifier: eissn: - 2691-3399 publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Tangent space generators of matrix product states and exact floquet quantum scars tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 317138e5-6ab7-11ef-aa6d-ffef3953e345 volume: 5 year: '2024' ... --- OA_place: publisher _id: '17208' abstract: - lang: eng text: "Can current quantum computers provide a speedup over their classical counterparts for some kinds of problems? In this thesis, with a focus on ground state search/preparation, we address some of the challenges that both quantum annealing and variational quantum algorithms suffer from, hindering any possible practical speedup in comparison to the best classical counterparts. \r\n\r\nIn the first part of the thesis, we study the performance of quantum annealing for solving a particular combinatorial optimization problem called 3-XOR satisfability (3-XORSAT). The classical problem is mapped into a ground state search of a 3-local classical Hamiltonian $H_C$. We consider how modifying the initial problem, by adding more interaction terms to the corresponding Hamiltonian, leads to the emergence of a first-order phase transition during the annealing process. This phenomenon causes the total annealing duration, $T$, required to prepare the ground state of $H_C$ with a high probability to increase exponentially with the size of the problem. Our findings indicate that with the growing complexity of problem instances, the likelihood of encountering first-order phase transitions also increases, making quantum annealing an impractical solution for these types of combinatorial optimization problems.\r\n\r\nIn the second part, we focus on the problem of barren plateaus in generic variational quantum algorithms. Barren plateaus correspond to flat regions in the parameter space where the gradient of the cost function is zero in expectation, and with the variance decaying exponentially with the system size, thus obstructing an efficient parameter optimization. We propose an algorithm to circumvent Barren Plateaus by monitoring the entanglement entropy of k-local reduced density matrices, alongside a method for estimating entanglement entropy via classical shadow tomography. We illustrate the approach with the paradigmatic example of the variational quantum eigensolver, and show that our algorithm effectively avoids barren plateaus in the initialization as well as during the optimization stage. \r\n\r\nLastly, in the last two Chapters of this thesis, we focus on the quantum approximate optimization algorithm (QAOA), originally introduced as an algorithm for solving generic combinatorial optimization problems in near-term quantum devices. Specifically, we focus on how to develop rigorous initialization strategies with guarantee improvement. Our motivation for this study lies in that for random initialization, the optimization typically leads to local minima with poor performance. Our main result corresponds to the analytical construction of index-1 saddle points or transition states, stationary points with a single direction of descent, as a tool for systematically exploring the QAOA optimization landscape. This leads us to propose a novel greedy parameter initialization strategy that guarantees for the energy to decrease with an increasing number of circuit layers. Furthermore, with precise estimates for the negative Hessian eigenvalue and its eigenvector, we establish a lower bound for energy improvement following a QAOA iteration." acknowledged_ssus: - _id: ScienComp alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Raimel A full_name: Medina Ramos, Raimel A id: CE680B90-D85A-11E9-B684-C920E6697425 last_name: Medina Ramos orcid: 0000-0002-5383-2869 citation: ama: Medina Ramos RA. Exploring the optimization landscape of variational quantum algorithms. 2024. doi:10.15479/at:ista:17208 apa: Medina Ramos, R. A. (2024). Exploring the optimization landscape of variational quantum algorithms. Institute of Science and Technology Austria. https://doi.org/10.15479/at:ista:17208 chicago: Medina Ramos, Raimel A. “Exploring the Optimization Landscape of Variational Quantum Algorithms.” Institute of Science and Technology Austria, 2024. https://doi.org/10.15479/at:ista:17208. ieee: R. A. Medina Ramos, “Exploring the optimization landscape of variational quantum algorithms,” Institute of Science and Technology Austria, 2024. ista: Medina Ramos RA. 2024. Exploring the optimization landscape of variational quantum algorithms. Institute of Science and Technology Austria. mla: Medina Ramos, Raimel A. Exploring the Optimization Landscape of Variational Quantum Algorithms. Institute of Science and Technology Austria, 2024, doi:10.15479/at:ista:17208. short: R.A. Medina Ramos, Exploring the Optimization Landscape of Variational Quantum Algorithms, Institute of Science and Technology Austria, 2024. corr_author: '1' date_created: 2024-07-09T09:14:24Z date_published: 2024-07-09T00:00:00Z date_updated: 2026-04-07T12:43:22Z day: '09' ddc: - '539' degree_awarded: PhD department: - _id: GradSch - _id: MaSe doi: 10.15479/at:ista:17208 ec_funded: 1 file: - access_level: closed checksum: 6f45273d04f4418bc2adc018baed0525 content_type: application/zip creator: rmedinar date_created: 2024-07-09T09:21:44Z date_updated: 2024-07-10T11:34:09Z file_id: '17212' file_name: Raimel_Thesis-Final.zip file_size: '14218691' relation: source_file - access_level: open_access checksum: 6724a95bec772dbabc0111b9f08a805e content_type: application/pdf creator: rmedinar date_created: 2024-07-17T09:23:24Z date_updated: 2024-07-17T09:23:24Z file_id: '17275' file_name: Raimel_Thesis-20_pdfa.pdf file_size: 11253627 relation: main_file success: 1 file_date_updated: 2024-07-17T09:23:24Z has_accepted_license: '1' keyword: - Quantum computing - Variational Quantum Algorithms - Optimization language: - iso: eng month: '07' oa: 1 oa_version: Published Version page: '133' project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '10545' relation: part_of_dissertation status: public - id: '10067' relation: part_of_dissertation status: public - id: '17222' relation: part_of_dissertation status: public - id: '13125' relation: part_of_dissertation status: public - id: '11471' relation: part_of_dissertation status: public status: public supervisor: - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 title: Exploring the optimization landscape of variational quantum algorithms tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: dissertation user_id: ba8df636-2132-11f1-aed0-ed93e2281fdd year: '2024' ... --- APC_amount: 4863,6 EUR DOAJ_listed: '1' OA_place: publisher OA_type: gold _id: '17493' abstract: - lang: eng text: Estimating global properties of many-body quantum systems such as entropy or bipartite entanglement is a notoriously difficult task, typically requiring a number of measurements or classical postprocessing resources growing exponentially in the system size. In this work, we address the problem of estimating global entropies and mixed-state entanglement via partial-transposed (PT) moments and show that efficient estimation strategies exist under the assumption that all the spatial correlation lengths are finite. Focusing on one-dimensional systems, we identify a set of approximate factorization conditions (AFCs) on the system density matrix, which allow us to reconstruct entropies and PT moments from information on local subsystems. This identification yields a simple and efficient strategy for entropy and entanglement estimation. Our method could be implemented in different ways, depending on how information on local subsystems is extracted. Focusing on randomized measurements providing a practical and common measurement scheme, we prove that our protocol requires only polynomially many measurements and postprocessing operations, assuming that the state to be measured satisfies the AFCs. We prove that the AFCs hold for finite-depth quantum-circuit states and translation-invariant matrix-product density operators and provide numerical evidence that they are satisfied in more general, physically interesting cases, including thermal states of local Hamiltonians. We argue that our method could be practically useful to detect bipartite mixed-state entanglement for large numbers of qubits available in today’s quantum platforms. acknowledgement: B. V. acknowledges funding from the Austrian Science Foundation (Grant No. FWF, P 32597 N), from the French National Research Agency via the JCJC project QRand (Grant No. ANR-20-CE47-0005), and via the research programs Plan France 2030 EPIQ (Grant No. ANR-22-PETQ-0007), QUBITAF (Grant No. ANR-22-PETQ-0004), and HQI (Grant No. ANR-22-PNCQ-0002). M. L. and M. S. acknowledge support by the European Research Council under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 850899). M. S. acknowledges the hospitality of KITP supported in part by the National Science Foundation under Grants No. NSF PHY-1748958 and No. NSF PHY-2309135. J. I. C. is supported by the Hightech Agenda Bayern Plus through the Munich Quantum Valley and the German Federal Ministry of Education and Research through EQUAHUMO (Grant No. 13N16066). P. Z. acknowledges funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 101113690 (PASQuanS2.1). article_number: '031035' article_processing_charge: Yes article_type: original arxiv: 1 author: - first_name: Benoît full_name: Vermersch, Benoît last_name: Vermersch - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 - first_name: J. Ignacio full_name: Cirac, J. Ignacio last_name: Cirac - first_name: Peter full_name: Zoller, Peter last_name: Zoller - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 - first_name: Lorenzo full_name: Piroli, Lorenzo last_name: Piroli citation: ama: Vermersch B, Ljubotina M, Cirac JI, Zoller P, Serbyn M, Piroli L. Many-body entropies and entanglement from polynomially many local measurements. Physical Review X. 2024;14(3). doi:10.1103/physrevx.14.031035 apa: Vermersch, B., Ljubotina, M., Cirac, J. I., Zoller, P., Serbyn, M., & Piroli, L. (2024). Many-body entropies and entanglement from polynomially many local measurements. Physical Review X. American Physical Society. https://doi.org/10.1103/physrevx.14.031035 chicago: Vermersch, Benoît, Marko Ljubotina, J. Ignacio Cirac, Peter Zoller, Maksym Serbyn, and Lorenzo Piroli. “Many-Body Entropies and Entanglement from Polynomially Many Local Measurements.” Physical Review X. American Physical Society, 2024. https://doi.org/10.1103/physrevx.14.031035. ieee: B. Vermersch, M. Ljubotina, J. I. Cirac, P. Zoller, M. Serbyn, and L. Piroli, “Many-body entropies and entanglement from polynomially many local measurements,” Physical Review X, vol. 14, no. 3. American Physical Society, 2024. ista: Vermersch B, Ljubotina M, Cirac JI, Zoller P, Serbyn M, Piroli L. 2024. Many-body entropies and entanglement from polynomially many local measurements. Physical Review X. 14(3), 031035. mla: Vermersch, Benoît, et al. “Many-Body Entropies and Entanglement from Polynomially Many Local Measurements.” Physical Review X, vol. 14, no. 3, 031035, American Physical Society, 2024, doi:10.1103/physrevx.14.031035. short: B. Vermersch, M. Ljubotina, J.I. Cirac, P. Zoller, M. Serbyn, L. Piroli, Physical Review X 14 (2024). date_created: 2024-09-04T18:57:11Z date_published: 2024-08-26T00:00:00Z date_updated: 2025-09-08T09:04:14Z day: '26' ddc: - '530' department: - _id: MaSe doi: 10.1103/physrevx.14.031035 ec_funded: 1 external_id: arxiv: - '2311.08108' isi: - '001299667100002' file: - access_level: open_access checksum: 1b114acc89025120727200681e4e9074 content_type: application/pdf creator: cchlebak date_created: 2024-09-05T09:39:00Z date_updated: 2024-09-05T09:39:00Z file_id: '17532' file_name: 2024_PhysRevX_Vermersch.pdf file_size: 1408836 relation: main_file success: 1 file_date_updated: 2024-09-05T09:39:00Z has_accepted_license: '1' intvolume: ' 14' isi: 1 issue: '3' language: - iso: eng month: '08' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: Physical Review X publication_identifier: issn: - 2160-3308 publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Many-body entropies and entanglement from polynomially many local measurements tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 317138e5-6ab7-11ef-aa6d-ffef3953e345 volume: 14 year: '2024' ... --- _id: '18110' abstract: - lang: eng text: We study a chaotic particle-conserving kinetically constrained model, with a single parameter which allows us to break reflection symmetry. Through extensive numerical simulations we find that the domain wall state shows a variety of dynamical behaviors from localization all the way to ballistic transport, depending on the value of the reflection breaking parameter. Surprisingly, such anomalous behavior is not mirrored in infinite-temperature dynamics, which appear to scale diffusively, in line with expectations for generic interacting models. However, studying the particle density gradient, we show that the lack of reflection symmetry affects infinite-temperature dynamics, resulting in an asymmetric dynamical structure factor. This is in disagreement with normal diffusion and suggests that the model may also exhibit anomalous dynamics at infinite temperature in the thermodynamic limit. Finally, we observe low-entangled eigenstates in the spectrum of the model, a telltale sign of quantum many-body scars. acknowledgement: "The authors acknowledge useful discussions with M. Serbyn, Z. Papic, and A. Nunnenkamp. ´\r\nP.B. is supported by the Erwin Schrödinger Center for Quantum Science & Technology (ESQ) of the Österreichische Akademie der Wissenschaften (ÖAW) under the Discovery Grant. M.L. acknowledges support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement\r\nNo. 850899). The numerical simulations were performed using the ITensor library [68] on the Vienna Scientific Cluster (VSC)." article_number: L100304 article_processing_charge: No article_type: letter_note arxiv: 1 author: - first_name: Pietro full_name: Brighi, Pietro id: 4115AF5C-F248-11E8-B48F-1D18A9856A87 last_name: Brighi orcid: 0000-0002-7969-2729 - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 citation: ama: Brighi P, Ljubotina M. Anomalous transport in the kinetically constrained quantum East-West model. Physical Review B. 2024;110(10). doi:10.1103/PhysRevB.110.L100304 apa: Brighi, P., & Ljubotina, M. (2024). Anomalous transport in the kinetically constrained quantum East-West model. Physical Review B. American Physical Society. https://doi.org/10.1103/PhysRevB.110.L100304 chicago: Brighi, Pietro, and Marko Ljubotina. “Anomalous Transport in the Kinetically Constrained Quantum East-West Model.” Physical Review B. American Physical Society, 2024. https://doi.org/10.1103/PhysRevB.110.L100304. ieee: P. Brighi and M. Ljubotina, “Anomalous transport in the kinetically constrained quantum East-West model,” Physical Review B, vol. 110, no. 10. American Physical Society, 2024. ista: Brighi P, Ljubotina M. 2024. Anomalous transport in the kinetically constrained quantum East-West model. Physical Review B. 110(10), L100304. mla: Brighi, Pietro, and Marko Ljubotina. “Anomalous Transport in the Kinetically Constrained Quantum East-West Model.” Physical Review B, vol. 110, no. 10, L100304, American Physical Society, 2024, doi:10.1103/PhysRevB.110.L100304. short: P. Brighi, M. Ljubotina, Physical Review B 110 (2024). corr_author: '1' date_created: 2024-09-22T22:01:42Z date_published: 2024-09-11T00:00:00Z date_updated: 2025-09-08T09:49:29Z day: '11' department: - _id: MaSe doi: 10.1103/PhysRevB.110.L100304 ec_funded: 1 external_id: arxiv: - '2405.02102' isi: - '001361617100003' intvolume: ' 110' isi: 1 issue: '10' language: - iso: eng main_file_link: - open_access: '1' url: https://doi.org/10.48550/arXiv.2405.02102 month: '09' oa: 1 oa_version: Preprint project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: Physical Review B publication_identifier: eissn: - 2469-9969 issn: - 2469-9950 publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Anomalous transport in the kinetically constrained quantum East-West model type: journal_article user_id: 317138e5-6ab7-11ef-aa6d-ffef3953e345 volume: 110 year: '2024' ... --- DOAJ_listed: '1' OA_place: publisher OA_type: gold _id: '18176' abstract: - lang: eng text: Introducing a class of SU(2) invariant quantum unitary circuits generating chiral transport, we examine the role of broken space-reflection and time-reversal symmetries on spin-transport properties. Upon adjusting parameters of local unitary gates, the dynamics can be either chaotic or integrable. The latter corresponds to a generalization of the space-time discretized (Trotterized) higher-spin quantum Heisenberg chain. We demonstrate that breaking of space-reflection symmetry results in a drift in the dynamical spin susceptibility. Remarkably, we find a universal drift velocity given by a simple formula, which, at zero average magnetization, depends only on the values of SU(2) Casimir invariants associated with local spins. In the integrable case, the drift velocity formula is confirmed analytically based on the exact solution of thermodynamic Bethe ansatz equations. Finally, by inspecting the large fluctuations of the time-integrated current between two halves of the system in stationary maximum-entropy states, we demonstrate violation of the Gallavotti-Cohen symmetry, implying that such states cannot be regarded as equilibrium ones. We show that the scaled cumulant generating function of the time-integrated current instead obeys a generalized fluctuation relation. acknowledgement: "The authors thank Denis Bernard, Jérôme Dubail, Hosho Katsura, Kareljan Schoutens, and Alberto Zorzato for stimulating discussions. This work has been supported by: Slovenian Research Agency (ARIS) under Grants No. N1-0219 (T.P., L.Z.), No. N1-0334 (T.P., L.Z.), No. N1-0243 (E.I.), and under Research Program P1-0402 (E.I., T.P., L.Z.). European Research Council (ERC) under Consolidator Grant No. 771536—NEMO (L.Z.), Advanced Grant No.\r\n101096208—QUEST (T.P., L.Z.), and Starting Grant No. 850899—NEQuM (M.L.). Simons Foundation under Simons Junior Fellowship Grant No. 1141511 (Ž.K.). M.L. acknowledges the hospitality of the Aspen Center for Physics, which is supported by National Science Foundation Grant No. PHY-2210452. Numerical simulations were performed using the ITensor library [117]. " article_number: '030356' article_processing_charge: Yes article_type: original arxiv: 1 author: - first_name: Lenart full_name: Zadnik, Lenart last_name: Zadnik - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 - first_name: Žiga full_name: Krajnik, Žiga last_name: Krajnik - first_name: Enej full_name: Ilievski, Enej last_name: Ilievski - first_name: Tomaž full_name: Prosen, Tomaž last_name: Prosen citation: ama: Zadnik L, Ljubotina M, Krajnik Ž, Ilievski E, Prosen T. Quantum many-body spin ratchets. PRX Quantum. 2024;5(3). doi:10.1103/PRXQuantum.5.030356 apa: Zadnik, L., Ljubotina, M., Krajnik, Ž., Ilievski, E., & Prosen, T. (2024). Quantum many-body spin ratchets. PRX Quantum. American Physical Society. https://doi.org/10.1103/PRXQuantum.5.030356 chicago: Zadnik, Lenart, Marko Ljubotina, Žiga Krajnik, Enej Ilievski, and Tomaž Prosen. “Quantum Many-Body Spin Ratchets.” PRX Quantum. American Physical Society, 2024. https://doi.org/10.1103/PRXQuantum.5.030356. ieee: L. Zadnik, M. Ljubotina, Ž. Krajnik, E. Ilievski, and T. Prosen, “Quantum many-body spin ratchets,” PRX Quantum, vol. 5, no. 3. American Physical Society, 2024. ista: Zadnik L, Ljubotina M, Krajnik Ž, Ilievski E, Prosen T. 2024. Quantum many-body spin ratchets. PRX Quantum. 5(3), 030356. mla: Zadnik, Lenart, et al. “Quantum Many-Body Spin Ratchets.” PRX Quantum, vol. 5, no. 3, 030356, American Physical Society, 2024, doi:10.1103/PRXQuantum.5.030356. short: L. Zadnik, M. Ljubotina, Ž. Krajnik, E. Ilievski, T. Prosen, PRX Quantum 5 (2024). date_created: 2024-10-06T22:01:12Z date_published: 2024-09-25T00:00:00Z date_updated: 2025-09-08T09:55:09Z day: '25' ddc: - '530' department: - _id: MaSe doi: 10.1103/PRXQuantum.5.030356 ec_funded: 1 external_id: arxiv: - '2406.01571' isi: - '001327172800001' file: - access_level: open_access checksum: bc230631255d3bcf8bcbbc8fdbfefcf2 content_type: application/pdf creator: dernst date_created: 2024-10-07T11:04:12Z date_updated: 2024-10-07T11:04:12Z file_id: '18183' file_name: 2024_PRXQuantum_Zadnik.pdf file_size: 1061648 relation: main_file success: 1 file_date_updated: 2024-10-07T11:04:12Z has_accepted_license: '1' intvolume: ' 5' isi: 1 issue: '3' language: - iso: eng month: '09' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: PRX Quantum publication_identifier: eissn: - 2691-3399 publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Quantum many-body spin ratchets tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 317138e5-6ab7-11ef-aa6d-ffef3953e345 volume: 5 year: '2024' ... --- OA_place: publisher _id: '12732' abstract: - lang: eng text: "Nonergodic systems, whose out-of-equilibrium dynamics fail to thermalize, provide a fascinating research direction both for fundamental reasons and for application in state of the art quantum devices.\r\nGoing beyond the description of statistical mechanics, ergodicity breaking yields a new paradigm in quantum many-body physics, introducing novel phases of matter with no counterpart at equilibrium.\r\nIn this Thesis, we address different open questions in the field, focusing on disorder-induced many-body localization (MBL) and on weak ergodicity breaking in kinetically constrained models.\r\nIn particular, we contribute to the debate about transport in kinetically constrained models, studying the effect of $U(1)$ conservation and inversion-symmetry breaking in a family of quantum East models.\r\nUsing tensor network techniques, we analyze the dynamics of large MBL systems beyond the limit of exact numerical methods.\r\nIn this setting, we approach the debated topic of the coexistence of localized and thermal eigenstates separated by energy thresholds known as many-body mobility edges.\r\nInspired by recent experiments, our work further investigates the localization of a small bath induced by the coupling to a large localized chain, the so-called MBL proximity effect.\r\n\r\nIn the first Chapter, we introduce a family of particle-conserving kinetically constrained models, inspired by the quantum East model.\r\nThe system we study features strong inversion-symmetry breaking, due to the nature of the correlated hopping.\r\nWe show that these models host so-called quantum Hilbert space fragmentation, consisting of disconnected subsectors in an entangled basis, and further provide an analytical description of this phenomenon.\r\nWe further probe its effect on dynamics of simple product states, showing revivals in fidelity and local observalbes.\r\nThe study of dynamics within the largest subsector reveals an anomalous transient superdiffusive behavior crossing over to slow logarithmic dynamics at later times.\r\nThis work suggests that particle conserving constrained models with inversion-symmetry breaking realize new universality classes of dynamics and invite their further theoretical and experimental studies.\r\n\r\nNext, we use kinetic constraints and disorder to design a model with many-body mobility edges in particle density.\r\nThis feature allows to study the dynamics of localized and thermal states in large systems beyond the limitations of previous studies.\r\nThe time-evolution shows typical signatures of localization at small densities, replaced by thermal behavior at larger densities.\r\nOur results provide evidence in favor of the stability of many-body mobility edges, which was recently challenged by a theoretical argument.\r\nTo support our findings, we probe the mechanism proposed as a cause of delocalization in many-body localized systems with mobility edges suggesting its ineffectiveness in the model studied.\r\n\r\nIn the last Chapter of this Thesis, we address the topic of many-body localization proximity effect.\r\nWe study a model inspired by recent experiments, featuring Anderson localized coupled to a small bath of free hard-core bosons.\r\nThe interaction among the two particle species results in non-trivial dynamics, which we probe using tensor network techniques.\r\nOur simulations show convincing evidence of many-body localization proximity effect when the bath is composed by a single free particle and interactions are strong.\r\nWe furthter observe an anomalous entanglement dynamics, which we explain through a phenomenological theory.\r\nFinally, we extract highly excited eigenstates of large systems, providing supplementary evidence in favor of our findings." acknowledged_ssus: - _id: ScienComp alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Pietro full_name: Brighi, Pietro id: 4115AF5C-F248-11E8-B48F-1D18A9856A87 last_name: Brighi orcid: 0000-0002-7969-2729 citation: ama: Brighi P. Ergodicity breaking in disordered and kinetically constrained quantum many-body systems. 2023. doi:10.15479/at:ista:12732 apa: Brighi, P. (2023). Ergodicity breaking in disordered and kinetically constrained quantum many-body systems. Institute of Science and Technology Austria. https://doi.org/10.15479/at:ista:12732 chicago: Brighi, Pietro. “Ergodicity Breaking in Disordered and Kinetically Constrained Quantum Many-Body Systems.” Institute of Science and Technology Austria, 2023. https://doi.org/10.15479/at:ista:12732. ieee: P. Brighi, “Ergodicity breaking in disordered and kinetically constrained quantum many-body systems,” Institute of Science and Technology Austria, 2023. ista: Brighi P. 2023. Ergodicity breaking in disordered and kinetically constrained quantum many-body systems. Institute of Science and Technology Austria. mla: Brighi, Pietro. Ergodicity Breaking in Disordered and Kinetically Constrained Quantum Many-Body Systems. Institute of Science and Technology Austria, 2023, doi:10.15479/at:ista:12732. short: P. Brighi, Ergodicity Breaking in Disordered and Kinetically Constrained Quantum Many-Body Systems, Institute of Science and Technology Austria, 2023. corr_author: '1' date_created: 2023-03-17T13:30:48Z date_published: 2023-03-21T00:00:00Z date_updated: 2026-04-07T13:26:32Z day: '21' ddc: - '530' degree_awarded: PhD department: - _id: GradSch - _id: MaSe doi: 10.15479/at:ista:12732 ec_funded: 1 file: - access_level: closed checksum: 5d2de651ef9449c1b8dc27148ca74777 content_type: application/zip creator: pbrighi date_created: 2023-03-23T16:42:56Z date_updated: 2023-03-23T16:42:56Z file_id: '12753' file_name: Thesis_sub_PBrighi.zip file_size: 42167561 relation: source_file - access_level: open_access checksum: 7caa153d4a5b0873a79358787d2dfe1e content_type: application/pdf creator: pbrighi date_created: 2023-03-23T16:43:14Z date_updated: 2023-03-23T16:43:14Z file_id: '12754' file_name: Thesis_PBrighi.pdf file_size: 13977000 relation: main_file success: 1 file_date_updated: 2023-03-23T16:43:14Z has_accepted_license: '1' language: - iso: eng license: https://creativecommons.org/licenses/by-nc-sa/4.0/ month: '03' oa: 1 oa_version: Published Version page: '158' project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '12750' relation: part_of_dissertation status: public - id: '11470' relation: part_of_dissertation status: public - id: '8308' relation: part_of_dissertation status: public - id: '11469' relation: part_of_dissertation status: public status: public supervisor: - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 title: Ergodicity breaking in disordered and kinetically constrained quantum many-body systems tmp: image: /images/cc_by_nc_sa.png legal_code_url: https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode name: Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) short: CC BY-NC-SA (4.0) type: dissertation user_id: ba8df636-2132-11f1-aed0-ed93e2281fdd year: '2023' ... --- _id: '12839' abstract: - lang: eng text: Universal nonequilibrium properties of isolated quantum systems are typically probed by studying transport of conserved quantities, such as charge or spin, while transport of energy has received considerably less attention. Here, we study infinite-temperature energy transport in the kinetically constrained PXP model describing Rydberg atom quantum simulators. Our state-of-the-art numerical simulations, including exact diagonalization and time-evolving block decimation methods, reveal the existence of two distinct transport regimes. At moderate times, the energy-energy correlation function displays periodic oscillations due to families of eigenstates forming different su(2) representations hidden within the spectrum. These families of eigenstates generalize the quantum many-body scarred states found in previous works and leave an imprint on the infinite-temperature energy transport. At later times, we observe a long-lived superdiffusive transport regime that we attribute to the proximity of a nearby integrable point. While generic strong deformations of the PXP model indeed restore diffusive transport, adding a strong chemical potential intriguingly gives rise to a well-converged superdiffusive exponent z≈3/2. Our results suggest constrained models to be potential hosts of novel transport regimes and call for developing an analytic understanding of their energy transport. acknowledgement: "We would like to thank Alexios Michailidis, Sarang Gopalakrishnan, and Achilleas Lazarides for useful comments. M. L. and M. S. acknowledge support by the European Research Council under the European Union’s Horizon 2020 research and innovation program (Grant\r\nAgreement No. 850899). J.-Y. D. and Z. P. acknowledge support by EPSRC Grant No. EP/R513258/1 and the Leverhulme Trust Research Leadership Grant No. RL2019-015. Statement of compliance with EPSRC policy framework on research data: This publication is theoretical work that does not require supporting research data. M. S., M. L., and Z. P. acknowledge support by the Erwin Schrödinger International Institute for Mathematics and\r\nPhysics. M. L. and M. S. acknowledge PRACE for awarding us access to Joliot-Curie at GENCI@CEA, France, where the TEBD simulations were performed. The TEBD\r\nsimulations were performed using the ITENSOR library [54]." article_number: '011033' article_processing_charge: No article_type: original author: - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 - first_name: Jean Yves full_name: Desaules, Jean Yves last_name: Desaules - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 - first_name: Zlatko full_name: Papić, Zlatko last_name: Papić citation: ama: Ljubotina M, Desaules JY, Serbyn M, Papić Z. Superdiffusive energy transport in kinetically constrained models. Physical Review X. 2023;13(1). doi:10.1103/PhysRevX.13.011033 apa: Ljubotina, M., Desaules, J. Y., Serbyn, M., & Papić, Z. (2023). Superdiffusive energy transport in kinetically constrained models. Physical Review X. American Physical Society. https://doi.org/10.1103/PhysRevX.13.011033 chicago: Ljubotina, Marko, Jean Yves Desaules, Maksym Serbyn, and Zlatko Papić. “Superdiffusive Energy Transport in Kinetically Constrained Models.” Physical Review X. American Physical Society, 2023. https://doi.org/10.1103/PhysRevX.13.011033. ieee: M. Ljubotina, J. Y. Desaules, M. Serbyn, and Z. Papić, “Superdiffusive energy transport in kinetically constrained models,” Physical Review X, vol. 13, no. 1. American Physical Society, 2023. ista: Ljubotina M, Desaules JY, Serbyn M, Papić Z. 2023. Superdiffusive energy transport in kinetically constrained models. Physical Review X. 13(1), 011033. mla: Ljubotina, Marko, et al. “Superdiffusive Energy Transport in Kinetically Constrained Models.” Physical Review X, vol. 13, no. 1, 011033, American Physical Society, 2023, doi:10.1103/PhysRevX.13.011033. short: M. Ljubotina, J.Y. Desaules, M. Serbyn, Z. Papić, Physical Review X 13 (2023). corr_author: '1' date_created: 2023-04-16T22:01:09Z date_published: 2023-03-07T00:00:00Z date_updated: 2025-04-14T07:52:07Z day: '07' ddc: - '530' department: - _id: MaSe doi: 10.1103/PhysRevX.13.011033 ec_funded: 1 external_id: isi: - '000957625700001' file: - access_level: open_access checksum: ee060cea609af79bba7af74b1ce28078 content_type: application/pdf creator: dernst date_created: 2023-04-17T08:36:53Z date_updated: 2023-04-17T08:36:53Z file_id: '12845' file_name: 2023_PhysReviewX_Ljubotina.pdf file_size: 1958523 relation: main_file success: 1 file_date_updated: 2023-04-17T08:36:53Z has_accepted_license: '1' intvolume: ' 13' isi: 1 issue: '1' language: - iso: eng month: '03' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: Physical Review X publication_identifier: eissn: - 2160-3308 publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Superdiffusive energy transport in kinetically constrained models tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 13 year: '2023' ... --- _id: '13963' abstract: - lang: eng text: The many-body localization (MBL) proximity effect is an intriguing phenomenon where a thermal bath localizes due to the interaction with a disordered system. The interplay of thermal and nonergodic behavior in these systems gives rise to a rich phase diagram, whose exploration is an active field of research. In this paper, we study a bosonic Hubbard model featuring two particle species representing the bath and the disordered system. Using state-of-the-art numerical techniques, we investigate the dynamics of the model in different regimes, based on which we obtain a tentative phase diagram as a function of coupling strength and bath size. When the bath is composed of a single particle, we observe clear signatures of a transition from an MBL proximity effect to a delocalized phase. Increasing the bath size, however, its thermalizing effect becomes stronger and eventually the whole system delocalizes in the range of moderate interaction strengths studied. In this regime, we characterize particle transport, revealing diffusive behavior of the originally localized bosons. acknowledgement: "We thank A. A. Michailidis and A. Mirlin for insightful discussions. P.B., M.L., and M.S. acknowledge support by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 850899). D.A. was\r\nsupported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 864597) and by the Swiss National Science Foundation. P.B., M.L., and M.S. acknowledge PRACE for awarding us access to Joliot-Curie at GENCI@CEA, France, where the TEBD simulations were performed. The TEBD simulations were performed using the ITensor library [60]." article_number: '054201' article_processing_charge: Yes (in subscription journal) article_type: original arxiv: 1 author: - first_name: Pietro full_name: Brighi, Pietro id: 4115AF5C-F248-11E8-B48F-1D18A9856A87 last_name: Brighi orcid: 0000-0002-7969-2729 - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 - first_name: Dmitry A. full_name: Abanin, Dmitry A. last_name: Abanin - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: Brighi P, Ljubotina M, Abanin DA, Serbyn M. Many-body localization proximity effect in a two-species bosonic Hubbard model. Physical Review B. 2023;108(5). doi:10.1103/physrevb.108.054201 apa: Brighi, P., Ljubotina, M., Abanin, D. A., & Serbyn, M. (2023). Many-body localization proximity effect in a two-species bosonic Hubbard model. Physical Review B. American Physical Society. https://doi.org/10.1103/physrevb.108.054201 chicago: Brighi, Pietro, Marko Ljubotina, Dmitry A. Abanin, and Maksym Serbyn. “Many-Body Localization Proximity Effect in a Two-Species Bosonic Hubbard Model.” Physical Review B. American Physical Society, 2023. https://doi.org/10.1103/physrevb.108.054201. ieee: P. Brighi, M. Ljubotina, D. A. Abanin, and M. Serbyn, “Many-body localization proximity effect in a two-species bosonic Hubbard model,” Physical Review B, vol. 108, no. 5. American Physical Society, 2023. ista: Brighi P, Ljubotina M, Abanin DA, Serbyn M. 2023. Many-body localization proximity effect in a two-species bosonic Hubbard model. Physical Review B. 108(5), 054201. mla: Brighi, Pietro, et al. “Many-Body Localization Proximity Effect in a Two-Species Bosonic Hubbard Model.” Physical Review B, vol. 108, no. 5, 054201, American Physical Society, 2023, doi:10.1103/physrevb.108.054201. short: P. Brighi, M. Ljubotina, D.A. Abanin, M. Serbyn, Physical Review B 108 (2023). corr_author: '1' date_created: 2023-08-05T18:25:22Z date_published: 2023-08-01T00:00:00Z date_updated: 2025-04-14T07:52:06Z day: '01' ddc: - '530' department: - _id: MaSe doi: 10.1103/physrevb.108.054201 ec_funded: 1 external_id: arxiv: - '2303.16876' file: - access_level: open_access checksum: f763000339b5fd543c14377109920690 content_type: application/pdf creator: dernst date_created: 2023-08-07T09:48:08Z date_updated: 2023-08-07T09:48:08Z file_id: '13981' file_name: 2023_PhysRevB_Brighi.pdf file_size: 3051398 relation: main_file success: 1 file_date_updated: 2023-08-07T09:48:08Z has_accepted_license: '1' intvolume: ' 108' issue: '5' language: - iso: eng month: '08' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: Physical Review B publication_identifier: eissn: - 2469-9969 issn: - 2469-9950 publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Many-body localization proximity effect in a two-species bosonic Hubbard model tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 108 year: '2023' ... --- _id: '14334' abstract: - lang: eng text: Quantum kinetically constrained models have recently attracted significant attention due to their anomalous dynamics and thermalization. In this work, we introduce a hitherto unexplored family of kinetically constrained models featuring conserved particle number and strong inversion-symmetry breaking due to facilitated hopping. We demonstrate that these models provide a generic example of so-called quantum Hilbert space fragmentation, that is manifested in disconnected sectors in the Hilbert space that are not apparent in the computational basis. Quantum Hilbert space fragmentation leads to an exponential in system size number of eigenstates with exactly zero entanglement entropy across several bipartite cuts. These eigenstates can be probed dynamically using quenches from simple initial product states. In addition, we study the particle spreading under unitary dynamics launched from the domain wall state, and find faster than diffusive dynamics at high particle densities, that crosses over into logarithmically slow relaxation at smaller densities. Using a classically simulable cellular automaton, we reproduce the logarithmic dynamics observed in the quantum case. Our work suggests that particle conserving constrained models with inversion symmetry breaking realize so far unexplored dynamical behavior and invite their further theoretical and experimental studies. acknowledgement: "We would like to thank Raimel A. Medina, Hansveer Singh, and Dmitry Abanin for useful\r\ndiscussions.The authors acknowledge support by the European Research Council\r\n(ERC) under the European Union’s Horizon 2020 research and innovation program (Grant\r\nAgreement No. 850899). We acknowledge support by the Erwin Schrödinger International\r\nInstitute for Mathematics and Physics (ESI)." article_number: '093' article_processing_charge: No article_type: original arxiv: 1 author: - first_name: Pietro full_name: Brighi, Pietro id: 4115AF5C-F248-11E8-B48F-1D18A9856A87 last_name: Brighi orcid: 0000-0002-7969-2729 - first_name: Marko full_name: Ljubotina, Marko id: F75EE9BE-5C90-11EA-905D-16643DDC885E last_name: Ljubotina orcid: 0000-0003-0038-7068 - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: Brighi P, Ljubotina M, Serbyn M. Hilbert space fragmentation and slow dynamics in particle-conserving quantum East models. SciPost Physics. 2023;15(3). doi:10.21468/scipostphys.15.3.093 apa: Brighi, P., Ljubotina, M., & Serbyn, M. (2023). Hilbert space fragmentation and slow dynamics in particle-conserving quantum East models. SciPost Physics. SciPost Foundation. https://doi.org/10.21468/scipostphys.15.3.093 chicago: Brighi, Pietro, Marko Ljubotina, and Maksym Serbyn. “Hilbert Space Fragmentation and Slow Dynamics in Particle-Conserving Quantum East Models.” SciPost Physics. SciPost Foundation, 2023. https://doi.org/10.21468/scipostphys.15.3.093. ieee: P. Brighi, M. Ljubotina, and M. Serbyn, “Hilbert space fragmentation and slow dynamics in particle-conserving quantum East models,” SciPost Physics, vol. 15, no. 3. SciPost Foundation, 2023. ista: Brighi P, Ljubotina M, Serbyn M. 2023. Hilbert space fragmentation and slow dynamics in particle-conserving quantum East models. SciPost Physics. 15(3), 093. mla: Brighi, Pietro, et al. “Hilbert Space Fragmentation and Slow Dynamics in Particle-Conserving Quantum East Models.” SciPost Physics, vol. 15, no. 3, 093, SciPost Foundation, 2023, doi:10.21468/scipostphys.15.3.093. short: P. Brighi, M. Ljubotina, M. Serbyn, SciPost Physics 15 (2023). corr_author: '1' date_created: 2023-09-14T13:08:23Z date_published: 2023-09-13T00:00:00Z date_updated: 2025-04-14T07:52:05Z day: '13' ddc: - '530' department: - _id: MaSe doi: 10.21468/scipostphys.15.3.093 ec_funded: 1 external_id: arxiv: - '2210.15607' file: - access_level: open_access checksum: 4cef6a8021f6b6c47ab2f2f2b1387ac2 content_type: application/pdf creator: dernst date_created: 2023-09-20T10:46:10Z date_updated: 2023-09-20T10:46:10Z file_id: '14350' file_name: 2023_SciPostPhysics_Brighi.pdf file_size: 4866506 relation: main_file success: 1 file_date_updated: 2023-09-20T10:46:10Z has_accepted_license: '1' intvolume: ' 15' issue: '3' keyword: - General Physics and Astronomy language: - iso: eng month: '09' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: SciPost Physics publication_identifier: issn: - 2542-4653 publication_status: published publisher: SciPost Foundation quality_controlled: '1' related_material: record: - id: '12750' relation: earlier_version status: public scopus_import: '1' status: public title: Hilbert space fragmentation and slow dynamics in particle-conserving quantum East models tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 15 year: '2023' ... --- OA_place: publisher _id: '14622' abstract: - lang: eng text: "This Ph.D. thesis presents a detailed investigation into Variational Quantum Algorithms\r\n(VQAs), a promising class of quantum algorithms that are well suited for near-term quantum\r\ncomputation due to their moderate hardware requirements and resilience to noise. Our\r\nprimary focus lies on two particular types of VQAs: the Quantum Approximate Optimization\r\nAlgorithm (QAOA), used for solving binary optimization problems, and the Variational Quantum\r\nEigensolver (VQE), utilized for finding ground states of quantum many-body systems.\r\nIn the first part of the thesis, we examine the issue of effective parameter initialization for\r\nthe QAOA. The work demonstrates that random initialization of the QAOA often leads to\r\nconvergence in local minima with sub-optimal performance. To mitigate this issue, we propose\r\nan initialization of QAOA parameters based on the Trotterized Quantum Annealing (TQA).\r\nWe show that TQA initialization leads to the same performance as the best of an exponentially\r\nscaling number of random initializations.\r\nThe second study introduces Transition States (TS), stationary points with a single direction\r\nof descent, as a tool for systematically exploring the QAOA optimization landscape. This\r\nleads us to propose a novel greedy parameter initialization strategy that guarantees for the\r\nenergy to decrease with increasing number of circuit layers.\r\nIn the third section, we extend the QAOA to qudit systems, which are higher-dimensional\r\ngeneralizations of qubits. This chapter provides theoretical insights and practical strategies for\r\nleveraging the increased computational power of qudits in the context of quantum optimization\r\nalgorithms and suggests a quantum circuit for implementing the algorithm on an ion trap\r\nquantum computer.\r\nFinally, we propose an algorithm to avoid “barren plateaus”, regions in parameter space with\r\nvanishing gradients that obstruct efficient parameter optimization. This novel approach relies\r\non defining a notion of weak barren plateaus based on the entropies of local reduced density\r\nmatrices and showcases how these can be efficiently quantified using shadow tomography.\r\nTo illustrate the approach we employ the strategy in the VQE and show that it allows to\r\nsuccessfully avoid barren plateaus in the initialization and throughout the optimization.\r\nTaken together, this thesis greatly enhances our understanding of parameter initialization and\r\noptimization in VQAs, expands the scope of QAOA to higher-dimensional quantum systems,\r\nand presents a method to address the challenge of barren plateaus using the VQE. These\r\ninsights are instrumental in advancing the field of near-term quantum computation." alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Stefan full_name: Sack, Stefan id: dd622248-f6e0-11ea-865d-ce382a1c81a5 last_name: Sack orcid: 0000-0001-5400-8508 citation: ama: 'Sack S. Improving variational quantum algorithms : Innovative initialization techniques and extensions to qudit systems. 2023. doi:10.15479/at:ista:14622' apa: 'Sack, S. (2023). Improving variational quantum algorithms : Innovative initialization techniques and extensions to qudit systems. Institute of Science and Technology Austria. https://doi.org/10.15479/at:ista:14622' chicago: 'Sack, Stefan. “Improving Variational Quantum Algorithms : Innovative Initialization Techniques and Extensions to Qudit Systems.” Institute of Science and Technology Austria, 2023. https://doi.org/10.15479/at:ista:14622.' ieee: 'S. Sack, “Improving variational quantum algorithms : Innovative initialization techniques and extensions to qudit systems,” Institute of Science and Technology Austria, 2023.' ista: 'Sack S. 2023. Improving variational quantum algorithms : Innovative initialization techniques and extensions to qudit systems. Institute of Science and Technology Austria.' mla: 'Sack, Stefan. Improving Variational Quantum Algorithms : Innovative Initialization Techniques and Extensions to Qudit Systems. Institute of Science and Technology Austria, 2023, doi:10.15479/at:ista:14622.' short: 'S. Sack, Improving Variational Quantum Algorithms : Innovative Initialization Techniques and Extensions to Qudit Systems, Institute of Science and Technology Austria, 2023.' corr_author: '1' date_created: 2023-11-28T10:58:13Z date_published: 2023-11-30T00:00:00Z date_updated: 2026-04-07T13:53:47Z day: '30' ddc: - '530' degree_awarded: PhD department: - _id: GradSch - _id: MaSe doi: 10.15479/at:ista:14622 ec_funded: 1 file: - access_level: open_access checksum: 068fd3570506ec42b2faa390de784bc4 content_type: application/pdf creator: ssack date_created: 2023-11-30T15:53:10Z date_updated: 2024-11-30T23:30:03Z embargo: 2024-11-30 file_id: '14635' file_name: PhD_Thesis.pdf file_size: 11947523 relation: main_file - access_level: closed checksum: 0fa3bc0d108aed0ac59d2c6beef2220a content_type: application/zip creator: ssack date_created: 2023-11-30T15:54:11Z date_updated: 2024-11-30T23:30:03Z embargo_to: open_access file_id: '14636' file_name: PhD Thesis (1).zip file_size: 18422964 relation: source_file file_date_updated: 2024-11-30T23:30:03Z has_accepted_license: '1' language: - iso: eng month: '11' oa: 1 oa_version: Published Version page: '142' project: - _id: bd660c93-d553-11ed-ba76-fb0fb6f49c0d name: IMB PhD Nomination Fellowship - Stefan Sack - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '13125' relation: part_of_dissertation status: public - id: '11471' relation: part_of_dissertation status: public - id: '9760' relation: part_of_dissertation status: public status: public supervisor: - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 title: 'Improving variational quantum algorithms : Innovative initialization techniques and extensions to qudit systems' tmp: image: /images/cc_by_nc_sa.png legal_code_url: https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode name: Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) short: CC BY-NC-SA (4.0) type: dissertation user_id: ba8df636-2132-11f1-aed0-ed93e2281fdd year: '2023' ... --- _id: '13125' abstract: - lang: eng text: 'The quantum approximate optimization algorithm (QAOA) is a variational quantum algorithm, where a quantum computer implements a variational ansatz consisting of p layers of alternating unitary operators and a classical computer is used to optimize the variational parameters. For a random initialization, the optimization typically leads to local minima with poor performance, motivating the search for initialization strategies of QAOA variational parameters. Although numerous heuristic initializations exist, an analytical understanding and performance guarantees for large p remain evasive.We introduce a greedy initialization of QAOA which guarantees improving performance with an increasing number of layers. Our main result is an analytic construction of 2p + 1 transition states—saddle points with a unique negative curvature direction—for QAOA with p + 1 layers that use the local minimum of QAOA with p layers. Transition states connect to new local minima, which are guaranteed to lower the energy compared to the minimum found for p layers. We use the GREEDY procedure to navigate the exponentially increasing with p number of local minima resulting from the recursive application of our analytic construction. The performance of the GREEDY procedure matches available initialization strategies while providing a guarantee for the minimal energy to decrease with an increasing number of layers p. ' acknowledgement: 'We thank V. Verteletskyi for a joint collaboration on numerical studies of the QAOA during his internship at ISTA that inspired analytic results on TS reported in this work. We acknowledge A. A. Mele and M. Brooks for discussions and D. Egger, P. Love, and D. Wierichs for valuable feedback on the manuscript. S.H.S., R.A.M., and M.S. acknowledge support by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 850899). R.K. is supported by the SFB BeyondC (Grant No. F7107-N38) and the project QuantumReady (FFG 896217). ' article_number: '062404' article_processing_charge: No article_type: original arxiv: 1 author: - first_name: Stefan full_name: Sack, Stefan id: dd622248-f6e0-11ea-865d-ce382a1c81a5 last_name: Sack orcid: 0000-0001-5400-8508 - first_name: Raimel A full_name: Medina Ramos, Raimel A id: CE680B90-D85A-11E9-B684-C920E6697425 last_name: Medina Ramos orcid: 0000-0002-5383-2869 - first_name: Richard full_name: Kueng, Richard last_name: Kueng - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: Sack S, Medina Ramos RA, Kueng R, Serbyn M. Recursive greedy initialization of the quantum approximate optimization algorithm with guaranteed improvement. Physical Review A. 2023;107(6). doi:10.1103/physreva.107.062404 apa: Sack, S., Medina Ramos, R. A., Kueng, R., & Serbyn, M. (2023). Recursive greedy initialization of the quantum approximate optimization algorithm with guaranteed improvement. Physical Review A. American Physical Society. https://doi.org/10.1103/physreva.107.062404 chicago: Sack, Stefan, Raimel A Medina Ramos, Richard Kueng, and Maksym Serbyn. “Recursive Greedy Initialization of the Quantum Approximate Optimization Algorithm with Guaranteed Improvement.” Physical Review A. American Physical Society, 2023. https://doi.org/10.1103/physreva.107.062404. ieee: S. Sack, R. A. Medina Ramos, R. Kueng, and M. Serbyn, “Recursive greedy initialization of the quantum approximate optimization algorithm with guaranteed improvement,” Physical Review A, vol. 107, no. 6. American Physical Society, 2023. ista: Sack S, Medina Ramos RA, Kueng R, Serbyn M. 2023. Recursive greedy initialization of the quantum approximate optimization algorithm with guaranteed improvement. Physical Review A. 107(6), 062404. mla: Sack, Stefan, et al. “Recursive Greedy Initialization of the Quantum Approximate Optimization Algorithm with Guaranteed Improvement.” Physical Review A, vol. 107, no. 6, 062404, American Physical Society, 2023, doi:10.1103/physreva.107.062404. short: S. Sack, R.A. Medina Ramos, R. Kueng, M. Serbyn, Physical Review A 107 (2023). corr_author: '1' date_created: 2023-06-07T06:57:32Z date_published: 2023-06-02T00:00:00Z date_updated: 2026-07-08T22:30:16Z day: '02' ddc: - '530' department: - _id: MaSe doi: 10.1103/physreva.107.062404 ec_funded: 1 external_id: arxiv: - '2209.01159' isi: - '001016927100012' file: - access_level: open_access checksum: 0d71423888eeccaa60d8f41197f26306 content_type: application/pdf creator: dernst date_created: 2023-06-13T07:28:36Z date_updated: 2023-06-13T07:28:36Z file_id: '13131' file_name: 2023_PhysRevA_Sack.pdf file_size: 2524611 relation: main_file success: 1 file_date_updated: 2023-06-13T07:28:36Z has_accepted_license: '1' intvolume: ' 107' isi: 1 issue: '6' language: - iso: eng month: '06' oa: 1 oa_version: Published Version project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: Physical Review A publication_identifier: eissn: - 2469-9934 issn: - 2469-9926 publication_status: published publisher: American Physical Society quality_controlled: '1' related_material: record: - id: '17208' relation: dissertation_contains status: public - id: '14622' relation: dissertation_contains status: public scopus_import: '1' status: public title: Recursive greedy initialization of the quantum approximate optimization algorithm with guaranteed improvement tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 107 year: '2023' ... --- _id: '11337' abstract: - lang: eng text: 'Nonanalytic points in the return probability of a quantum state as a function of time, known as dynamical quantum phase transitions (DQPTs), have received great attention in recent years, but the understanding of their mechanism is still incomplete. In our recent work [Phys. Rev. Lett. 126, 040602 (2021)], we demonstrated that one-dimensional DQPTs can be produced by two distinct mechanisms, namely semiclassical precession and entanglement generation, leading to the definition of precession (pDQPTs) and entanglement (eDQPTs) dynamical quantum phase transitions. In this manuscript, we extend and investigate the notion of p- and eDQPTs in two-dimensional systems by considering semi-infinite ladders of varying width. For square lattices, we find that pDQPTs and eDQPTs persist and are characterized by similar phenomenology as in 1D: pDQPTs are associated with a magnetization sign change and a wide entanglement gap, while eDQPTs correspond to suppressed local observables and avoided crossings in the entanglement spectrum. However, DQPTs show higher sensitivity to the ladder width and other details, challenging the extrapolation to the thermodynamic limit especially for eDQPTs. Moving to honeycomb lattices, we also demonstrate that lattices with an odd number of nearest neighbors give rise to phenomenologies beyond the one-dimensional classification.' acknowledgement: "We acknowledge support by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 850899).\r\nS.D.N. also acknowledges funding from the Institute of Science and Technology (IST) Austria, and from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie Grant Agreement No. 754411." article_number: '165149' article_processing_charge: No article_type: original arxiv: 1 author: - first_name: Stefano full_name: De Nicola, Stefano id: 42832B76-F248-11E8-B48F-1D18A9856A87 last_name: De Nicola orcid: 0000-0002-4842-6671 - first_name: Alexios full_name: Michailidis, Alexios id: 36EBAD38-F248-11E8-B48F-1D18A9856A87 last_name: Michailidis orcid: 0000-0002-8443-1064 - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: De Nicola S, Michailidis A, Serbyn M. Entanglement and precession in two-dimensional dynamical quantum phase transitions. Physical Review B. 2022;105. doi:10.1103/PhysRevB.105.165149 apa: De Nicola, S., Michailidis, A., & Serbyn, M. (2022). Entanglement and precession in two-dimensional dynamical quantum phase transitions. Physical Review B. American Physical Society. https://doi.org/10.1103/PhysRevB.105.165149 chicago: De Nicola, Stefano, Alexios Michailidis, and Maksym Serbyn. “Entanglement and Precession in Two-Dimensional Dynamical Quantum Phase Transitions.” Physical Review B. American Physical Society, 2022. https://doi.org/10.1103/PhysRevB.105.165149. ieee: S. De Nicola, A. Michailidis, and M. Serbyn, “Entanglement and precession in two-dimensional dynamical quantum phase transitions,” Physical Review B, vol. 105. American Physical Society, 2022. ista: De Nicola S, Michailidis A, Serbyn M. 2022. Entanglement and precession in two-dimensional dynamical quantum phase transitions. Physical Review B. 105, 165149. mla: De Nicola, Stefano, et al. “Entanglement and Precession in Two-Dimensional Dynamical Quantum Phase Transitions.” Physical Review B, vol. 105, 165149, American Physical Society, 2022, doi:10.1103/PhysRevB.105.165149. short: S. De Nicola, A. Michailidis, M. Serbyn, Physical Review B 105 (2022). corr_author: '1' date_created: 2022-04-28T08:06:10Z date_published: 2022-04-15T00:00:00Z date_updated: 2025-04-14T07:43:57Z day: '15' department: - _id: MaSe doi: 10.1103/PhysRevB.105.165149 ec_funded: 1 external_id: arxiv: - '2112.11273' isi: - '000806812400004' intvolume: ' 105' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: ' https://doi.org/10.48550/arXiv.2112.11273' month: '04' oa: 1 oa_version: Preprint project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' - _id: 260C2330-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '754411' name: ISTplus - Postdoctoral Fellowships publication: Physical Review B publication_identifier: eisbn: - 2469-9969 issn: - 2469-9950 publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Entanglement and precession in two-dimensional dynamical quantum phase transitions type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 105 year: '2022' ... --- _id: '11469' abstract: - lang: eng text: Thermalizing and localized many-body quantum systems present two distinct dynamical phases of matter. Recently the fate of a localized system coupled to a thermalizing system viewed as a quantum bath received significant theoretical and experimental attention. In this work, we study a mobile impurity, representing a small quantum bath, that interacts locally with an Anderson insulator with a finite density of localized particles. Using static Hartree approximation to obtain an effective disorder strength, we formulate an analytic criterion for the perturbative stability of the localization. Next, we use an approximate dynamical Hartree method and the quasi-exact time-evolved block decimation (TEBD) algorithm to study the dynamics of the system. We find that the dynamical Hartree approach which completely ignores entanglement between the impurity and localized particles predicts the delocalization of the system. In contrast, the full numerical simulation of the unitary dynamics with TEBD suggests the stability of localization on numerically accessible timescales. Finally, using an extension of the density matrix renormalization group algorithm to excited states (DMRG-X), we approximate the highly excited eigenstates of the system. We find that the impurity remains localized in the eigenstates and entanglement is enhanced in a finite region around the position of the impurity, confirming the dynamical predictions. Dynamics and the DMRG-X results provide compelling evidence for the stability of localization. acknowledged_ssus: - _id: ScienComp acknowledgement: We thank M. Ljubotina for insightful discussions. P. B., A. M. and M. S. acknowledge support by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 850899). D. A. was supported by the Swiss National Science Foundation and by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 864597). The development of parallel TEBD code was supported by S. Elefante from the Scientific Computing (SciComp) that is part of Scientific Service Units (SSU) of IST Austria. Some of the computations were performed on the Baobab cluster of the University of Geneva. article_number: '224208' article_processing_charge: No article_type: original arxiv: 1 author: - first_name: Pietro full_name: Brighi, Pietro id: 4115AF5C-F248-11E8-B48F-1D18A9856A87 last_name: Brighi orcid: 0000-0002-7969-2729 - first_name: Alexios full_name: Michailidis, Alexios id: 36EBAD38-F248-11E8-B48F-1D18A9856A87 last_name: Michailidis orcid: 0000-0002-8443-1064 - first_name: Kristina full_name: Kirova, Kristina id: 4aeda2ae-f847-11ec-98e0-c4a66fe174d4 last_name: Kirova - first_name: Dmitry A. full_name: Abanin, Dmitry A. last_name: Abanin - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: Brighi P, Michailidis A, Kirova K, Abanin DA, Serbyn M. Localization of a mobile impurity interacting with an Anderson insulator. Physical Review B. 2022;105(22). doi:10.1103/physrevb.105.224208 apa: Brighi, P., Michailidis, A., Kirova, K., Abanin, D. A., & Serbyn, M. (2022). Localization of a mobile impurity interacting with an Anderson insulator. Physical Review B. American Physical Society. https://doi.org/10.1103/physrevb.105.224208 chicago: Brighi, Pietro, Alexios Michailidis, Kristina Kirova, Dmitry A. Abanin, and Maksym Serbyn. “Localization of a Mobile Impurity Interacting with an Anderson Insulator.” Physical Review B. American Physical Society, 2022. https://doi.org/10.1103/physrevb.105.224208. ieee: P. Brighi, A. Michailidis, K. Kirova, D. A. Abanin, and M. Serbyn, “Localization of a mobile impurity interacting with an Anderson insulator,” Physical Review B, vol. 105, no. 22. American Physical Society, 2022. ista: Brighi P, Michailidis A, Kirova K, Abanin DA, Serbyn M. 2022. Localization of a mobile impurity interacting with an Anderson insulator. Physical Review B. 105(22), 224208. mla: Brighi, Pietro, et al. “Localization of a Mobile Impurity Interacting with an Anderson Insulator.” Physical Review B, vol. 105, no. 22, 224208, American Physical Society, 2022, doi:10.1103/physrevb.105.224208. short: P. Brighi, A. Michailidis, K. Kirova, D.A. Abanin, M. Serbyn, Physical Review B 105 (2022). corr_author: '1' date_created: 2022-06-29T20:19:51Z date_published: 2022-06-27T00:00:00Z date_updated: 2026-04-07T13:26:31Z day: '27' department: - _id: MaSe doi: 10.1103/physrevb.105.224208 ec_funded: 1 external_id: arxiv: - '2111.08603' isi: - '000823050000001' intvolume: ' 105' isi: 1 issue: '22' language: - iso: eng main_file_link: - open_access: '1' url: ' https://doi.org/10.48550/arXiv.2111.08603' month: '06' oa: 1 oa_version: Preprint project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: Physical Review B publication_identifier: eissn: - 2469-9969 issn: - 2469-9950 publication_status: published publisher: American Physical Society quality_controlled: '1' related_material: record: - id: '12732' relation: dissertation_contains status: public scopus_import: '1' status: public title: Localization of a mobile impurity interacting with an Anderson insulator type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 105 year: '2022' ... --- _id: '11470' abstract: - lang: eng text: Many-body localization (MBL) is an example of a dynamical phase of matter that avoids thermalization. While the MBL phase is robust to weak local perturbations, the fate of an MBL system coupled to a thermalizing quantum system that represents a “heat bath” is an open question that is actively investigated theoretically and experimentally. In this work, we consider the stability of an Anderson insulator with a finite density of particles interacting with a single mobile impurity—a small quantum bath. We give perturbative arguments that support the stability of localization in the strong interaction regime. Large-scale tensor network simulations of dynamics are employed to corroborate the presence of the localized phase and give quantitative predictions in the thermodynamic limit. We develop a phenomenological description of the dynamics in the strong interaction regime, and we demonstrate that the impurity effectively turns the Anderson insulator into an MBL phase, giving rise to nontrivial entanglement dynamics well captured by our phenomenology. acknowledged_ssus: - _id: ScienComp acknowledgement: We acknowledge useful discussions with M. Ljubotina. P. B., A. M., and M. S. were supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 850899). D.A. was supported by the Swiss National Science Foundation and by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 864597). The development of parallel TEBD code was was supported by S. Elefante from the Scientific Computing (SciComp) that is part of Scientific Service Units (SSU) of IST Austria. Some of the computations were performed on the Baobab cluster of the University of Geneva. article_number: L220203 article_processing_charge: No article_type: original arxiv: 1 author: - first_name: Pietro full_name: Brighi, Pietro id: 4115AF5C-F248-11E8-B48F-1D18A9856A87 last_name: Brighi orcid: 0000-0002-7969-2729 - first_name: Alexios A. full_name: Michailidis, Alexios A. last_name: Michailidis - first_name: Dmitry A. full_name: Abanin, Dmitry A. last_name: Abanin - first_name: Maksym full_name: Serbyn, Maksym id: 47809E7E-F248-11E8-B48F-1D18A9856A87 last_name: Serbyn orcid: 0000-0002-2399-5827 citation: ama: Brighi P, Michailidis AA, Abanin DA, Serbyn M. Propagation of many-body localization in an Anderson insulator. Physical Review B. 2022;105(22). doi:10.1103/physrevb.105.l220203 apa: Brighi, P., Michailidis, A. A., Abanin, D. A., & Serbyn, M. (2022). Propagation of many-body localization in an Anderson insulator. Physical Review B. American Physical Society. https://doi.org/10.1103/physrevb.105.l220203 chicago: Brighi, Pietro, Alexios A. Michailidis, Dmitry A. Abanin, and Maksym Serbyn. “Propagation of Many-Body Localization in an Anderson Insulator.” Physical Review B. American Physical Society, 2022. https://doi.org/10.1103/physrevb.105.l220203. ieee: P. Brighi, A. A. Michailidis, D. A. Abanin, and M. Serbyn, “Propagation of many-body localization in an Anderson insulator,” Physical Review B, vol. 105, no. 22. American Physical Society, 2022. ista: Brighi P, Michailidis AA, Abanin DA, Serbyn M. 2022. Propagation of many-body localization in an Anderson insulator. Physical Review B. 105(22), L220203. mla: Brighi, Pietro, et al. “Propagation of Many-Body Localization in an Anderson Insulator.” Physical Review B, vol. 105, no. 22, L220203, American Physical Society, 2022, doi:10.1103/physrevb.105.l220203. short: P. Brighi, A.A. Michailidis, D.A. Abanin, M. Serbyn, Physical Review B 105 (2022). corr_author: '1' date_created: 2022-06-29T20:20:47Z date_published: 2022-06-27T00:00:00Z date_updated: 2026-04-07T13:26:31Z day: '27' department: - _id: MaSe doi: 10.1103/physrevb.105.l220203 ec_funded: 1 external_id: arxiv: - '2109.07332' isi: - '000823050000012' intvolume: ' 105' isi: 1 issue: '22' language: - iso: eng main_file_link: - open_access: '1' url: ' https://doi.org/10.48550/arXiv.2109.07332' month: '06' oa: 1 oa_version: Preprint project: - _id: 23841C26-32DE-11EA-91FC-C7463DDC885E call_identifier: H2020 grant_number: '850899' name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control' publication: Physical Review B publication_identifier: eissn: - 2469-9969 issn: - 2469-9950 publication_status: published publisher: American Physical Society quality_controlled: '1' related_material: record: - id: '12732' relation: dissertation_contains status: public scopus_import: '1' status: public title: Propagation of many-body localization in an Anderson insulator type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 105 year: '2022' ...