Abstract
Circuit quantum electrodynamics, where photons are coherently coupled to artificial atoms built with superconducting circuits, has enabled the investigation and control of macroscopic quantum-mechanical phenomena in superconductors. Recently, hybrid circuits incorporating semiconducting nanowires and other electrostatically-gateable elements have provided new insights into mesoscopic superconductivity. Extending the capabilities of hybrid flux-based circuits to work in magnetic fields would be especially useful both as a probe of spin-polarized Andreev bound states and as a possible platform for topological qubits. The fluxonium is particularly suitable as a readout circuit for topological qubits due to its unique persistent-current based eigenstates. In this Letter, we present a magnetic-field compatible hybrid fluxonium with an electrostatically-tuned semiconducting nanowire as its non-linear element. We operate the fluxonium in magnetic fields up to 1T and use it to observe the $\varphi_0$-Josephson effect. This combination of gate-tunability and field-compatibility opens avenues for the exploration and control of spin-polarized phenomena using superconducting circuits and enables the use of the fluxonium as a readout device for topological qubits.
Highlights
Circuit quantum electrodynamics, where photons are coherently coupled to artificial atoms built with superconducting circuits, has enabled the investigation and control of macroscopic quantum-mechanical phenomena in superconductors [1,2,3]
In superconductor-proximitized semiconductors exposed to a large magnetic field, emergent quasiparticle states known as Majorana zero modes (MZMs) can form
Our linewidth analysis indicates that the energy resolution of the fluxonium would, if measuring near φext = 0, be at most 0.4 μeV in all regimes, which significantly improves upon the resolution that can currently be reached by transport experiments where the linewidth is limited by thermal broadening
Summary
Circuit quantum electrodynamics (cQED), where photons are coherently coupled to artificial atoms built with superconducting circuits, has enabled the investigation and control of macroscopic quantum-mechanical phenomena in superconductors [1,2,3]. In superconductor-proximitized semiconductors exposed to a large magnetic field, emergent quasiparticle states known as Majorana zero modes (MZMs) can form. Links would be an extremely useful tool both for investigating the magnetic field behavior of ABSs and for coupling to topological superconductors. We build upon recent work proximitizing semiconducting nanowires to incorporate a magnetic-field compatible, electrostatically tunable weak-link junction into the fluxonium [32]. We demonstrate the utility of the fluxonium as a probe of mesoscopic superconductivity in magnetic fields by using the measured energy-phase relation of the junction to observe the φ0-Josephson effect.
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