Phonon-Mediated Quasiparticle Poisoning of Superconducting Microwave Resonators

TL;DR

This paper investigates how phonons mediate quasiparticle poisoning in superconducting microwave resonators, revealing the propagation mechanism, energy dependence, and how quasiparticle traps can significantly reduce quasiparticle loss.

Contribution

It demonstrates that phonon propagation dominates quasiparticle poisoning and shows that normal metal traps can greatly mitigate quasiparticle loss in superconducting devices.

Findings

Quasiparticle poisoning is dominated by phonon propagation.

Energy dependence of poisoning timescales characterized.

Normal metal traps reduce quasiparticle loss by over an order of magnitude.

Abstract

Nonequilibrium quasiparticles represent a significant source of decoherence in superconducting quantum circuits. Here we investigate the mechanism of quasiparticle poisoning in devices subjected to local quasiparticle injection. We find that quasiparticle poisoning is dominated by the propagation of pair-breaking phonons across the chip. We characterize the energy dependence of the timescale for quasiparticle poisoning. Finally, we observe that incorporation of extensive normal metal quasiparticle traps leads to a more than order of magnitude reduction in quasiparticle loss for a given injected quasiparticle power.