---
OA_place: publisher
_id: '21863'
abstract:
- lang: eng
text: "Atoms and photons, two things so different but yet so alike. The former,
the building block of matter, something we learn about in school and imagine it
as some tiny marbles encircled by other tinier marbles. The latter, an electromagnetic
wave, a light particle or an excitation of the electromagnetic field. Quantum
mechanics tells us about the properties of these two entities. And even if it
sounds, looks and writes counter-intuitive, it has proven right for over a century
now.\r\n\r\nIn this work, I elaborate on how we tested the laws of quantum mechanics
and how we used them learn more about the tiny building blocks of nature and the
fields they use to talk to each other. The atoms we use, are artificial. Superconducting
qubits, small electrical circuits with quantized energy levels behave like electrons
that transition between different orbitals in an atom. One of the qubits' advantages,
is also a big disadvantage. We design the circuits' energy levels and fabricate
them in a cleanroom. This allows for arbitrary spaced energy levels but in contrast
to real atoms, prevents two superconducting qubits from being alike. Still, this
qubit platform is one of the frontrunners for future quantum computing technology
and testing fundamental physics due to their scalability.\r\n\r\nWe interface
superconducting qubits, which operate in the GHz regime, with microwave photons.
We use 3D aluminum cavities as mediators between qubits and photons. The cavities
allow for non-destructive readout of the qubit state, they shield the qubits from
noise at the qubit frequency and they give us an easy way to frequency-tune these
joint systems.\r\n\r\nWe need to operate superconducting qubits and their cavities
at millikelvin temperatures in dilution refrigerators. At higher temperatures,
superconductivity suffers and even worse, the environment is filled with thermal
noise photons. This poses a fundamental limitation on the scalability of superconducting
qubit devices. Also connecting multiple devices in different fridges does not
work over room temperature links because the microwave photons used for this purpose
will be covered in noise and the quantum information they carry, will be unusable.\r\n\r\nInfrared
photons do not suffer from this noise problem since there are close to zero thermal
noise photons at their frequencies at room temperature. We cannot simply interface
superconducting devices with optical photons due their frequency mismatch and
the destructive effect of optical photons on superconductors. Therefore, we use
microwave-to-optics transducers that allow to convert microwave photons into optical
ones and vice-versa. The transducers that we use are macroscopic electro-optic
transducers using the Pockels effect in a disk-shaped Lithium Niobate whispering
gallery mode resonator. By using a strong optical pump, photons from the two frequency
domains experience a beam-splitter interaction and get converted from one to the
other.\r\n\r\nWe measure the generated optical photons using elaborate optical
setups, optical heterodyning and single photon detectors to gain knowledge about
the qubit state or the converted microwave photons. Bridging the microwave and
the optical world allows us to take advantage of both of their strengths but it
also requires deep knowledge about both of their working principles.\r\n\r\nIn
this work, we describe two experiments that our group conducted to showcase the
opportunities that arise from interfacing superconducting qubits with optical
photons but also the pitfalls, one may encounter on the way.\r\n\r\nIn the first
experiment, we managed to all-optically read out a superconducting qubit. We show
that the assignment fidelity, the probability that a measurement of the qubit
state matches the prepared state, is close to equal for all-optical, microwave-to-optics
and conventional microwave readout. We show T1 and T2 measurements for all three
readout types and give an analysis of the noise caused by the optics. Finally,
we show that the infrared light does not affect the qubit performance in a negative
way but that the heating it causes does. This is an important insight that we
used in the next experiment.\r\n\r\nThe second experiment is the upconversion
of itinerant single microwave photons to the optical domain. We show that we can
generate single microwave photons from a qubit-cavity system. We upconvert these
single photons, measure them with a single photon detector and reconstruct their
shape. By conducting a single photon Rabi measurement, we show correlations between
the microwave and the optical domain. And by thorough signal-to-noise measurements
and noise analysis, we find that we can generate single infrared photons with
high signal-to-noise ratio 5.1 and low transducer added noise (<0.012 quanta).
We show that this measurement creates a path towards entanglement of a superconducting
qubit and an optical photon and what parameters need to be improved to achieve
it. Additionally, this experiment is a proof of principle for an on-demand infrared
single photon source. More generally, it allows to link microwave quantum technology
in general to the optical domain."
acknowledged_ssus:
- _id: M-Shop
- _id: NanoFab
- _id: LifeSc
- _id: SSU
acknowledgement: "The author of this work was supported by the European Research Council
under grant no.\r\n101089099 (ERC CoG cQEO) and the European Union’s Horizon 2020
research and innovation\r\nprogram under grant no. 899354 (FETopen SuperQuLAN).\r\nThis
work was also supported by the European Research Council under grant nos. 758053\r\n(ERC
StG QUNNECT), 101248662 (ERC POC CoupledEOT), and the European Innovation\r\nCouncil
no. 101187231 (PathfinderOpen CIELO). This research was funded in whole or in part\r\nby
the Austrian Science Fund (FWF) [10.55776/F71]. For open access purposes, the author\r\nhas
applied a CC BY public copyright license to any author accepted manuscript version
arising\r\nfrom this submission.\r\niii\r\nMy co-authors in the works mentioned
later acknowledge generous support from the ISTFELLOW program, the NOMIS-ISTA fellowship,
the Horizon Europe Program HORIZONCL4-2022-QUANTUM-01-SGA via Project No. 101113946
OpenSuperQPlus100 and a DOC fellowship of the Austrian Academy of Sciences at IST
Austria.\r\n"
alternative_title:
- ISTA Thesis
article_processing_charge: No
author:
- first_name: Thomas
full_name: Werner, Thomas
id: 1fcd8497-dba3-11ea-a45e-c6fbd715f7c7
last_name: Werner
orcid: 0009-0001-2346-5236
citation:
ama: Werner T. Interfacing superconducting qubits with optical photons. 2026. doi:10.15479/AT-ISTA-21863
apa: Werner, T. (2026). Interfacing superconducting qubits with optical photons.
Institute of Science and Technology Austria. https://doi.org/10.15479/AT-ISTA-21863
chicago: Werner, Thomas. “Interfacing Superconducting Qubits with Optical Photons.”
Institute of Science and Technology Austria, 2026. https://doi.org/10.15479/AT-ISTA-21863.
ieee: T. Werner, “Interfacing superconducting qubits with optical photons,” Institute
of Science and Technology Austria, 2026.
ista: Werner T. 2026. Interfacing superconducting qubits with optical photons. Institute
of Science and Technology Austria.
mla: Werner, Thomas. Interfacing Superconducting Qubits with Optical Photons.
Institute of Science and Technology Austria, 2026, doi:10.15479/AT-ISTA-21863.
short: T. Werner, Interfacing Superconducting Qubits with Optical Photons, Institute
of Science and Technology Austria, 2026.
corr_author: '1'
date_created: 2026-05-12T09:04:02Z
date_published: 2026-05-12T00:00:00Z
date_updated: 2026-05-20T13:35:43Z
day: '12'
ddc:
- '530'
- '537'
- '539'
degree_awarded: PhD
department:
- _id: GradSch
- _id: JoFi
doi: 10.15479/AT-ISTA-21863
ec_funded: 1
file:
- access_level: open_access
checksum: a5b4d8dba83f96e955a3625c0eebee98
content_type: application/pdf
creator: twerner
date_created: 2026-05-15T15:53:57Z
date_updated: 2026-05-15T15:53:57Z
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date_created: 2026-05-15T15:54:06Z
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file_name: 2026_Werner_Thomas_Thesis.zip
file_size: 9370704
relation: source_file
file_date_updated: 2026-05-15T15:54:06Z
has_accepted_license: '1'
keyword:
- Superconducting qubits
- Quantum optics
- Single photons and quantum effects
- Nonlinear optics
language:
- iso: eng
license: https://creativecommons.org/licenses/by/4.0/
month: '05'
oa: 1
oa_version: Published Version
page: '97'
project:
- _id: bdadfa0d-d553-11ed-ba76-fb85edbd456a
grant_number: '101089099'
name: 'Cavity Quantum Electro Optics: Microwave photonics with nonclassical states'
- _id: 9B868D20-BA93-11EA-9121-9846C619BF3A
call_identifier: H2020
grant_number: '899354'
name: Quantum Local Area Networks with Superconducting Qubits
- _id: 26336814-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '758053'
name: A Fiber Optic Transceiver for Superconducting Qubits
- _id: 5b807754-ab3d-11f0-914f-ff8c34502cc9
grant_number: '101248662'
name: Integrated optical coupling for low loss electro-optic interconnects
- _id: 91aaf765-16d5-11f0-9cad-a8e7e44cccb7
grant_number: '101187231'
name: 'Cavity-Integrated Electro-Optics: Measuring, Converting and Manipulating
Microwaves with Light'
- _id: bdb108fd-d553-11ed-ba76-83dc74a9864f
grant_number: F07105
name: QUANTUM INFORMATION SYSTEMS BEYOND CLASSICAL CAPABILITIES / P5- Integration
of Superconducting Quantum Circuits
- _id: bdb7cfc1-d553-11ed-ba76-d2eaab167738
grant_number: '101080139'
name: Open Superconducting Quantum Computers (OpenSuperQPlus)
- _id: 9B861AAC-BA93-11EA-9121-9846C619BF3A
name: NOMIS Fellowship Program
publication_identifier:
issn:
- 2663-337X
publication_status: published
publisher: Institute of Science and Technology Austria
related_material:
record:
- id: '19073'
relation: part_of_dissertation
status: public
- id: '21870'
relation: part_of_dissertation
status: public
status: public
supervisor:
- first_name: Johannes M
full_name: Fink, Johannes M
id: 4B591CBA-F248-11E8-B48F-1D18A9856A87
last_name: Fink
orcid: 0000-0001-8112-028X
title: Interfacing superconducting qubits with optical photons
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: 8b945eb4-e2f2-11eb-945a-df72226e66a9
year: '2026'
...
---
OA_place: repository
OA_type: green
_id: '21870'
abstract:
- lang: eng
text: Superconducting qubits are a leading candidate for utility-scale quantum computing
due to their fast gate speeds and steadily decreasing error rates. The requirement
for millikelvin operating temperatures, however, creates a significant scaling
bottleneck. Modular architectures using optical fiber links could bridge separate
cryogenic nodes, but superconducting circuits do not have coherent optical transitions
and microwave-to-optical conversion has not been shown for any non-classical photon
state. In this work, we demonstrate the on-demand generation and tomographic reconstruction
of itinerant single microwave photons at 8.9 GHz from a superconducting qubit.
We upconvert this non-Gaussian state with a transducer added noise below 0.012
quanta and count the converted telecom photons at 193.4 THz with a signal-to-noise
ratio of up to 5.1$\pm$1.1. We characterize the trade-offs between throughput
and noise, and establish a viable path toward heralded entanglement distribution
and gate teleportation. Looking ahead, these results empower existing superconducting
devices to take a key role in distributed quantum technologies and heterogeneous
quantum systems.
acknowledgement: "We thank Fritz Diorico and Onur Hosten who suggested the filter
cavity design, and gave important insights about the assembly and the testing of
the FabryPerot filter cavities. Ekatrina Fedotova and Diego A.\r\nLancheros Naranjo
worked on the filter cavity setup in\r\nthe early stages of this work. Gustavo Wiederhecker
and\r\nYiewen Chu provided insights as to the origins of the\r\nobserved optical
noise and Nicola Carlon Zambon suggested using telecom filters to mitigate it further.
This\r\nwork was supported by the European Research Council under grant agreement
no. 101089099 (ERC CoG\r\ncQEO), and 101248662 (ERC POC CoupledEOT), the\r\nEuropean
Unions Horizon 2020 research and innovation\r\nprogram under grant agreement no.
899354 (FETopen\r\nSuperQuLAN), the European Innovation Council no.\r\n101187231
(PathfinderOpen CIELO), and the Austrian\r\nScience Fund (FWF) no. F7105 (SFB BeyondC).
J.F.\r\nand L.K. acknowledge support from the Horizon Europe\r\nProgram HORIZON-CL4-2022-QUANTUM-01-SGA
via\r\nProject No. 101113946 OpenSuperQPlus100. A.M. acknowledges support from the
NOMIS-ISTA fellowship."
article_processing_charge: No
arxiv: 1
author:
- first_name: Thomas
full_name: Werner, Thomas
id: 1fcd8497-dba3-11ea-a45e-c6fbd715f7c7
last_name: Werner
orcid: 0009-0001-2346-5236
- first_name: Erfan
full_name: Riyazi, Erfan
id: 53322f94-5355-11ee-ae5a-ff6f81c87d51
last_name: Riyazi
- first_name: Samarth
full_name: Hawaldar, Samarth
id: 221708e1-1ff6-11ee-9fa6-85146607433e
last_name: Hawaldar
orcid: 0000-0002-1965-4309
- first_name: Rishabh
full_name: Sahu, Rishabh
id: 47D26E34-F248-11E8-B48F-1D18A9856A87
last_name: Sahu
orcid: 0000-0001-6264-2162
- first_name: Georg M
full_name: Arnold, Georg M
id: 3770C838-F248-11E8-B48F-1D18A9856A87
last_name: Arnold
orcid: 0000-0003-1397-7876
- first_name: Paul Falthansl-Scheinecker
full_name: Paul Falthansl-Scheinecker, Paul Falthansl-Scheinecker
last_name: Paul Falthansl-Scheinecker
- first_name: Jennifer A. Sánchez
full_name: Naranjo, Jennifer A. Sánchez
last_name: Naranjo
- first_name: Dante
full_name: Loi, Dante
last_name: Loi
- first_name: Lucky N.
full_name: Kapoor, Lucky N.
last_name: Kapoor
- first_name: Martin
full_name: Zemlicka, Martin
id: 2DCF8DE6-F248-11E8-B48F-1D18A9856A87
last_name: Zemlicka
orcid: 0009-0005-0878-3032
- first_name: Liu
full_name: Qiu, Liu
id: 45e99c0d-1eb1-11eb-9b96-ed8ab2983cac
last_name: Qiu
orcid: 0000-0003-4345-4267
- first_name: Andrei
full_name: Militaru, Andrei
id: d67706f8-8eb1-11ee-ad1b-9c30dfa19e0b
last_name: Militaru
- first_name: Johannes M
full_name: Fink, Johannes M
id: 4B591CBA-F248-11E8-B48F-1D18A9856A87
last_name: Fink
orcid: 0000-0001-8112-028X
citation:
ama: Werner T, Riyazi E, Hawaldar S, et al. Electro-optic conversion of itinerant
Fock states. arXiv. doi:10.48550/arXiv.2602.00928
apa: Werner, T., Riyazi, E., Hawaldar, S., Sahu, R., Arnold, G. M., Paul Falthansl-Scheinecker,
P. F.-S., … Fink, J. M. (n.d.). Electro-optic conversion of itinerant Fock states.
arXiv. https://doi.org/10.48550/arXiv.2602.00928
chicago: Werner, Thomas, Erfan Riyazi, Samarth Hawaldar, Rishabh Sahu, Georg M Arnold,
Paul Falthansl-Scheinecker Paul Falthansl-Scheinecker, Jennifer A. Sánchez Naranjo,
et al. “Electro-Optic Conversion of Itinerant Fock States.” ArXiv, n.d.
https://doi.org/10.48550/arXiv.2602.00928.
ieee: T. Werner et al., “Electro-optic conversion of itinerant Fock states,”
arXiv. .
ista: Werner T, Riyazi E, Hawaldar S, Sahu R, Arnold GM, Paul Falthansl-Scheinecker
PF-S, Naranjo JAS, Loi D, Kapoor LN, Zemlicka M, Qiu L, Militaru A, Fink JM. Electro-optic
conversion of itinerant Fock states. arXiv, 10.48550/arXiv.2602.00928.
mla: Werner, Thomas, et al. “Electro-Optic Conversion of Itinerant Fock States.”
ArXiv, doi:10.48550/arXiv.2602.00928.
short: T. Werner, E. Riyazi, S. Hawaldar, R. Sahu, G.M. Arnold, P.F.-S. Paul Falthansl-Scheinecker,
J.A.S. Naranjo, D. Loi, L.N. Kapoor, M. Zemlicka, L. Qiu, A. Militaru, J.M. Fink,
ArXiv (n.d.).
corr_author: '1'
date_created: 2026-05-12T13:58:18Z
date_published: 2026-01-31T00:00:00Z
date_updated: 2026-05-20T13:35:42Z
day: '31'
department:
- _id: JoFi
- _id: GradSch
doi: 10.48550/arXiv.2602.00928
ec_funded: 1
external_id:
arxiv:
- '2602.00928'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://doi.org/10.48550/arXiv.2602.00928
month: '01'
oa: 1
oa_version: Preprint
project:
- _id: bdadfa0d-d553-11ed-ba76-fb85edbd456a
grant_number: '101089099'
name: 'Cavity Quantum Electro Optics: Microwave photonics with nonclassical states'
- _id: 5b807754-ab3d-11f0-914f-ff8c34502cc9
grant_number: '101248662'
name: Integrated optical coupling for low loss electro-optic interconnects
- _id: 9B868D20-BA93-11EA-9121-9846C619BF3A
call_identifier: H2020
grant_number: '899354'
name: Quantum Local Area Networks with Superconducting Qubits
- _id: 91aaf765-16d5-11f0-9cad-a8e7e44cccb7
grant_number: '101187231'
name: 'Cavity-Integrated Electro-Optics: Measuring, Converting and Manipulating
Microwaves with Light'
- _id: 26927A52-B435-11E9-9278-68D0E5697425
call_identifier: FWF
grant_number: F07105
name: Integrating superconducting quantum circuits
- _id: 9B861AAC-BA93-11EA-9121-9846C619BF3A
name: NOMIS Fellowship Program
publication: arXiv
publication_status: draft
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title: Electro-optic conversion of itinerant Fock states
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: preprint
user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9
year: '2026'
...