Josephson junctions are the basis for the most sensitive magnetic flux detectors, the definition of the unit volt by the Josephson voltage standard, and superconducting digital and quantum computing.They result from the coupling of two coherent quantum states, as they occur in superconductors, superfluids, atomic Bose Einstein Condensates (BECs), and exciton-polariton condensates.In their ground state, Josephson junctions are characterized by an intrinsic phase jump.Controlling this phase jump is fundamental for applications in computing.Here, we experimentally demonstrate controllable phase relations between photon BECs resulting from particle exchange in a thermo-optically tunable potential landscape.Our experiment realizes an optical analog of a controllable 0,π -Josephson junction.By connecting several junctions, we can study a reconfigurable 4-condensate system demonstrating the potential of our approach for analog spin-glass simulation.More generally, the combination of static and dynamic nanostructuring techniques introduced in our work offers a powerful platform for the implementation of adaptive optical systems for paraxial light in and outside of thermal equilibrium.Josephson junctions are the basis for the most sensitive magnetic flux detectors, the definition of the unit volt by the Josephson voltage standard, and superconducting digital and quantum computing.They result from the coupling of two coherent quantum states, as they occur in superconductors, superfluids, atomic Bose Einstein Condensates (BECs), and exciton-polariton condensates.In their ground state, Josephson junctions are characterized by an intrinsic phase jump.Controlling this phase jump is fundamental for applications in computing.Here, we experimentally demonstrate controllable phase relations between photon BECs resulting from particle exchange in a thermo-optically tunable potential landscape.Our experiment realizes an optical analog of a controllable 0,π -Josephson junction.By connecting several junctions, we can study a reconfigurable 4-condensate system demonstrating the potential of our approach for analog spin-glass simulation.More generally, the combination of static and dynamic nanostructuring techniques introduced in our work offers a powerful platform for the implementation of adaptive optical systems for paraxial light in and outside of thermal equilibrium.

arXiv:2001.09828Physical Review ResearchJun 1, 202135 citations

Phase-controllable thermal routing with Josephson circuits

Federico Paolucci, Giuliano Timossi, Antonio Fornieri +2 more

Bulletin of the American Physical SocietyMar 9, 20180 citations

MATBG Josephson diode as an universal thermal machine

Hadi Mohammed Soufy, Colin Benjamin

Magic-angle twisted bilayer graphene Josephson junctions (MATBG-JJ) with a gate-tunable valley-polarized weak link exhibit an intrinsic Josephson diode effect originating from broken symmetries associated with valley polarization and band-structure anisotropy. Exploiting this nonreciprocal superconducting platform, we construct quantum Stirling (QSC), Otto (QOC), and Carnot (QCC) thermodynamic cycles, where the valley-polarization potential $Δ_v$ acts as the principal control parameter, in contrast to conventional Josephson thermal machines driven by superconducting phase bias. We systematically compare the performance of MATBG-based Josephson diode thermal machines (MATBG-JDTM) with MATBG-based Josephson junction thermal machines (MATBG-JJTM) and AA-stacked bilayer graphene Josephson junction thermal machines (AABLG-JJTM). Owing to the flat-band-enhanced density of states and electrically tunable nonreciprocal transport in MATBG, both MATBG-JDTM and MATBG-JJTM exhibit significantly enhanced work output and efficiency over a broad operating regime compared to AABLG-JJTM. In particular, the gate-controlled MATBG-JDTM provides a flux-free alternative to conventional phase-driven architectures, mitigating limitations associated with magnetic-flux control and flux-noise effects. Our results establish MATBG Josephson diode platforms as a promising route toward electrically tunable quantum thermal machines and nonreciprocal superconducting caloritronics.Magic-angle twisted bilayer graphene Josephson junctions (MATBG-JJ) with a gate-tunable valley-polarized weak link exhibit an intrinsic Josephson diode effect originating from broken symmetries associated with valley polarization and band-structure anisotropy. Exploiting this nonreciprocal superconducting platform, we construct quantum Stirling (QSC), Otto (QOC), and Carnot (QCC) thermodynamic cycles, where the valley-polarization potential $Δ_v$ acts as the principal control parameter, in contrast to conventional Josephson thermal machines driven by superconducting phase bias. We systematically compare the performance of MATBG-based Josephson diode thermal machines (MATBG-JDTM) with MATBG-based Josephson junction thermal machines (MATBG-JJTM) and AA-stacked bilayer graphene Josephson junction thermal machines (AABLG-JJTM). Owing to the flat-band-enhanced density of states and electrically tunable nonreciprocal transport in MATBG, both MATBG-JDTM and MATBG-JJTM exhibit significantly enhanced work output and efficiency over a broad operating regime compared to AABLG-JJTM. In particular, the gate-controlled MATBG-JDTM provides a flux-free alternative to conventional phase-driven architectures, mitigating limitations associated with magnetic-flux control and flux-noise effects. Our results establish MATBG Josephson diode platforms as a promising route toward electrically tunable quantum thermal machines and nonreciprocal superconducting caloritronics.

cond-mat.mes-hallCross-listedarXiv:2605.27560May 28, 2026

Δ_v

acts as the principal control parameter, in contrast to conventional Josephson thermal machines driven by superconducting phase bias. We systematically compare the performance of MATBG-based Josephson diode thermal machines (MATBG-JDTM) with MATBG-based Josephson junction thermal machines (MATBG-JJTM) and AA-stacked bilayer graphene Josephson junction thermal machines (AABLG-JJTM). Owing to the flat-band-enhanced density of states and electrically tunable nonreciprocal transport in MATBG, both MATBG-JDTM and MATBG-JJTM exhibit significantly enhanced work output and efficiency over a broad operating regime compared to AABLG-JJTM. In particular, the gate-controlled MATBG-JDTM provides a flux-free alternative to conventional phase-driven architectures, mitigating limitations associated with magnetic-flux control and flux-noise effects. Our results establish MATBG Josephson diode platforms as a promising route toward electrically tunable quantum thermal machines and nonreciprocal superconducting caloritronics.