Quantum dot Josephson junction in a hybrid superconductor-semiconductor transmon device: a novel route for Andreev qubits.*

This talk will focus on the physics of 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 very good agreement with that predicted by the superconducting single-impurity Anderson model. Interestingly, the quasiparticle dynamics reveal very long parity lifetimes which, together with spin-orbit induced spin splitting of the doublet manifold, hold promise towards realizing Andreev qubits based on superconducting quantum dots.