Non-equilibrium quasiparticle trapping in epitaxial Al-InAs Josephson junctions

Planar epitaxial Al-InAs Josephson junctions (JJs) offer a unique platform for realizing tunable qubits and have shown signatures of topological superconductivity with the promise of hosting fault-tolerant qubits. In such high-transparency JJs, non-equilibrium quasiparticles can get trapped in the Andreev bound states of the junction, poisoning conduction channels. While quasiparticle poisoning can limit a parity-based qubit's coherence, it can also be harnessed to store information in the spin of a trapped quasiparticle forming a superconducting spin qubit. We study quasiparticle poisoning events by terminating a superconducting resonator to ground with an Al-InAs two-junction superconducting quantum interference device (SQUID). We investigate for signatures of quasiparticle poisoning in the resonant frequency of the resonator when the junction is flux-biased. Further, we perform continuous detection of these quasiparticle trapping events using time-domain measurements. Our results highlight the potential and limitations of quasiparticle poisoning in superconducting circuits based on Al-InAs JJs.