Direct microwave measurement of Andreev-bound-state dynamics in a proximitized semiconducting nanowire

TL;DR

This paper demonstrates microwave detection and real-time tracking of Andreev-bound-state dynamics in a proximitized semiconducting nanowire, revealing parity-switching events and implications for topological quantum computing.

Contribution

It introduces a microwave circuit QED method to coherently manipulate and monitor Andreev bound states in gate-tunable nanowire junctions, advancing quantum control techniques.

Findings

Observed individual parity-switching events with a timescale of 160 microseconds.

Demonstrated real-time tracking of Andreev bound state fermion parity.

Set a lower bound on control bandwidth for Majorana bound states in topological nanowires.

Abstract

The modern understanding of the Josephson effect in mesosopic devices derives from the physics of Andreev bound states, fermionic modes that are localized in a superconducting weak link. Recently, Josephson junctions constructed using semiconducting nanowires have led to the realization of superconducting qubits with gate-tunable Josephson energies. We have used a microwave circuit QED architecture to detect Andreev bound states in such a gate-tunable junction based on an aluminum-proximitized InAs nanowire. We demonstrate coherent manipulation of these bound states, and track the bound-state fermion parity in real time. Individual parity-switching events due to non-equilibrium quasiparticles are observed with a characteristic timescale $T_\mathrm{parity} = 160\pm 10~\mathrm{\mu s}$. The $T_\mathrm{parity}$ of a topological nanowire junction sets a lower bound on the bandwidth required for control of Majorana bound states.