@article{21340,
  abstract     = {Equilibrium quantum systems are often described by a gas of weakly interacting normal modes. Bringing such systems far from equilibrium, however, can drastically enhance mode-to-mode interactions. Understanding the resulting liquid is a fundamental question for quantum statistical mechanics and a practical question for engineering driven quantum devices. To tackle this question, we probe the non-equilibrium kinetics of one-dimensional plasmons in a long chain of Josephson junctions. We introduce multimode spectroscopy to controllably study the departure from equilibrium, witnessing the evolution from pairwise coupling between plasma modes at weak driving to dramatic, high-order, cascaded couplings at strong driving. Scaling to many-mode drives, we stimulate interactions between hundreds of modes, resulting in near-continuum internal dynamics. Imaging the resulting non-equilibrium plasmon populations, we then resolve the nonlocal redistribution of energy in the response to a weak perturbation—an explicit verification of the emergence of a strongly interacting, non-equilibrium liquid of plasmons.},
  author       = {Bubis, Anton and Vigliotti, Lucia and Serbyn, Maksym and Higginbotham, Andrew P},
  issn         = {2375-2548},
  journal      = {Science Advances},
  number       = {7},
  publisher    = {American Association for the Advancement of Science},
  title        = {{Non-equilibrium plasmon liquid in a Josephson junction chain}},
  doi          = {10.1126/sciadv.ady7222},
  volume       = {12},
  year         = {2026},
}

@article{22323,
  abstract     = {Arrays of Josephson junctions can be tuned through anomalous metallic, quantum-critical, and insulating regimes. We introduce an alternative experimental probe, capturing microwave radiation across all three regimes, using a two-dimensional array of superconductor-semiconductor hybrid Josephson junctions as a model system. Our approach allows  calibration of the sample’s circuit parameters and provides isolation from measurement back-action effects. We measure the radiation temperature of the anomalous metal and find that it is hotter than both the quantum-critical and insulating regimes. We further show that the anomalous metallic regime is more susceptible to additional heating than other regimes, explaining its emergence in otherwise thermalized systems. Turning to the quantum-critical regime, we discover nonlinear scaling of radiative noise with applied bias, consistent with theoretical predictions of universal nonequilibrium behavior at quantum-critical points.},
  author       = {Galvin, Kristen W and Bubis, Anton and Mikalsen, Melissa and Schiela, William F. and Elfeky, Bassel H. and Strickland, William M. and Phan, Duc T and Shabani, Javad and Higginbotham, Andrew P},
  issn         = {2331-7019},
  journal      = {Physical Review Applied},
  publisher    = {American Physical Society},
  title        = {{Microwave radiometry of a quantum-critical hybrid Josephson array}},
  doi          = {10.1103/75bl-mm3b},
  volume       = {26},
  year         = {2026},
}

@article{22619,
  abstract     = {Planar germanium is currently the only semiconducting platform where high-coherence spin qubits and proximity-induced superconductivity have each been demonstrated. Recent research into spin qubits in Ge/SiGe heterostructures has focused on increasing the thickness of the SiGe capping layer, reporting improvements in the electrostatic noise levels. Meanwhile, heterostructures with thinner capping layers remain rather unexplored, despite the potential advantages for proximity-induced superconductivity. Here, we study a Ge/SiGe heterostructure with a thin SiGe cap d - 4nm and investigate its viability to host low-noise quantum dots. To keep the thermal budget compatible with superconducting layers, low-temperature oxide deposition processes were developed and implemented for the gate dielectrics. The charge noise level of the fabricated devices is estimated to be 1.8  +- 1.0 μeV/ square HZ⁠, comparable to devices fabricated on shallow heterostructures (⁠ d - 20nm⁠) with high-temperature deposited oxides. Low charge noise levels, together with the straightforward integration of superconductors, make this heterostructure an attractive platform for prototyping hybrid semiconducting–superconducting devices.},
  author       = {Borovkov, Maksim and Schell, Yona A and Sokolova, Dina and Roux, Kevin Etienne Robert and Falthansl-Scheinecker, Paul and Fabris, Giorgio and Shah, Devashish C and Saez Mollejo, Jaime and Previdi, Rodolfo and Taha, Inas and Genç, Aziz and Arbiol, Jordi and Calcaterra, Stefano and Oliveira, Afonso De Cerdeira and Chrastina, Daniel and Isella, Giovanni and Bubis, Anton and Katsaros, Georgios},
  issn         = {1077-3118},
  journal      = {Applied Physics Letters},
  number       = {3},
  publisher    = {AIP Publishing},
  title        = {{Low-noise quantum dots in ultra-shallow Ge/SiGe heterostructures for prototyping hybrid semiconducting–superconducting devices}},
  doi          = {10.1063/5.0333142},
  volume       = {129},
  year         = {2026},
}