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We realize a hybrid superconductor-semiconductor transmon device in which the Josephson effect is controlled by a gate-defined quantum dot in an InAs/Al nanowire. Microwave spectroscopy of the transmon's transition spectrum allows us to probe the ground state parity of the quantum dot as a function of gate voltages, external magnetic flux, and magnetic field applied parallel to the nanowire. The measured parity phase diagram is in agreement with that predicted by a single-impurity Anderson model with superconducting leads. Through continuous time monitoring of the circuit we furthermore resolve the quasiparticle dynamics of the quantum dot Josephson junction across the phase boundaries. Our results can facilitate the realization of semiconductor-based $0-\pi$ qubits and Andreev qubits., Comment: Main text has 14 pages, 7 figures. Supplement has 21 pages, 21 figures

We report the detection of a gate-tunable kinetic inductance in a hybrid InAs/Al nanowire. For this purpose, we have embedded the nanowire into a quarter-wave coplanar waveguide resonator and measured the resonance frequency of the circuit. We find that the resonance frequency can be changed via the gate voltage that controls the electron density of the proximitized semiconductor and thus the nanowire inductance. Applying Mattis-Bardeen theory, we extract the gate dependence of the normal state conductivity of the nanowire, as well as its superconducting gap. Our measurements complement existing characterization methods for hybrid nanowires and provide a new and useful tool for gate-controlled superconducting electronics.

The tunneling of quasiparticles (QPs) across Josephson junctions (JJs) detrimentally affects the coherence of superconducting and charge-parity qubits, and is shown to occur more frequently in magnetic fields. Here we demonstrate the parity lifetime to survive in excess of 50$\,\mathrm{\mu}$s in magnetic fields up to 1$\,$T, utilising a semiconducting nanowire transmon to detect QP tunneling in real time. We exploit gate-tunable QP filters and find magnetic-field-enhanced parity lifetimes, consistent with increased QP trapping by the ungated nanowire due to orbital effects. Our findings highlight the importance of QP trap engineering for building magnetic-field compatible hybrid superconducting circuits., Comment: 12 pages, 11 figures

Josephson junctions in InAs nanowires proximitized with an Al shell can host gate-tunable Andreev bound states. Depending on the bound state occupation, the fermion parity of the junction can be even or odd. Coherent control of Andreev bound states has recently been achieved within each parity sector, but it is impeded by incoherent parity switches due to excess quasiparticles in the superconducting environment. Here, we show that we can polarize the fermion parity dynamically using microwave pulses by embedding the junction in a superconducting LC resonator. We demonstrate polarization up to 94% $\pm$ 1% (89% $\pm$ 1%) for the even (odd) parity as verified by single shot parity-readout. Finally, we apply this scheme to probe the flux-dependent transition spectrum of the even or odd parity sector selectively, without any post-processing or heralding.

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.

We study the effect of gate-induced electric fields on the properties of semiconductor-superconductor hybrid nanowires which represent a promising platform for realizing topological superconductivity and Majorana zero modes. Using a self-consistent Schr\"odinger-Poisson approach that describes the semiconductor and the superconductor on equal footing, we are able to access the strong tunneling regime and identify the impact of an applied gate voltage on the coupling between semiconductor and superconductor. We discuss how physical parameters such as the induced superconducting gap and Land\'e g-factor in the semiconductor are modified by redistributing the density of states across the interface upon application of an external gate voltage. Finally, we map out the topological phase diagram as a function of magnetic field and gate voltage for InAs/Al nanowires., Comment: 19 pages, 16 figures; added section "Effect of disorder in SC-SM heterostructures"

Experimental autoimmune orchitis (EAO) was induced in inbred strains of mice by injection of mouse testis homogenate (MTH) in Freund’s complete adjuvant with pertussis vaccine. Although all mice injected with MTH and adjuvants developed signs of EAO, there were marked strain variations in susceptibility to EAO suggesting that genetic factors may be involved in the response to antigen or to adjuvants. Studies in hypothymic BALB/c. nu/nu mice indicated that a source of T cell was required for induction of EAO. Thus BALB/c. nu/nu mice were not able to develop EAO, despite adequate orchitogenic challenge; reconstitution of nu/nu mice with syngeneic thymocytes completely restored the capacity of such mice to develop orchitis. Transfer of EAO was effected in nu/nu mice with lymphoid cells from appropriately immunized donors but not with immune serum. However, both T cells and antibodies may be necessary in the effector stages of the disease since the capacity of lymphoid cells to transfer EAO was only partially inhibited by anti-Thy-1.2 treatment.