Andreev bound state dynamics in phase- and gate-tunable InAs Nanowire Josephson weak links

Localized fermionic modes called Andreev bound states (ABSs) in InAs nanowire - superconductor weak links have been utilized in the past to realize Andreev pair and spin qubits [1, 2]. The occupation of ABSs is not only controlled by microwave drive tones, it also varies due to pair recombination, quasiparticle poisoning, relaxation and excitation. In general, several configurations of the ABS occupations are involved. From the measurement of how Andreev qubits relax to the steady state after an excitation pulse, we extract the transition rates between configurations and analyse their dependence on the phase across the weak link and on the gate voltage controlling the electronic properties of the nanowire weak link.

References:

1. M. Hays et al., Direct Microwave Measurement of AndreevBound-State Dynamics in a Semiconductor-Nanowire Josephson Junction, Phys. Rev. Lett. 121, 047001 (2018).

2. M. Hays et al., Coherent manipulation of an Andreev spin qubit, Science 373, 430 (2021).