Qubit error bursts in superconducting quantum processors of Quantum Inspire: quasiparticle pumping and anomalous time dependence

TL;DR

This study examines qubit error bursts in superconducting quantum processors, revealing device-specific behaviors linked to quasiparticle dynamics and unexpected long-term error rate fluctuations.

Contribution

It identifies novel signatures of error bursts related to quasiparticle pumping and long-term time dependence in superconducting qubits with different junction types.

Findings

Error burst characteristics vary with device and are consistent with ionizing radiation effects.

Quasiparticle pumping shortens recovery times with increased $ ext{p}$ pulsing.

Long-term error rate surges occur weeks after cooldown and are suppressed by thermal cycling.

Abstract

We investigate qubit error bursts in 5- and 7-transmon processors of similar design, fabrication and packaging, but with different types of qubit Josephson junctions. Measurements for each are performed in two refrigerators to discern device-specific from refrigerator-dependent characteristics. The duration and rate of bursts are device specific but within the range of prior experiments and consistent with ionizing radiation. We observe two unforeseen signatures specifically in the processor with Dolan junctions. First, increasing the rate of $\pi$ pulsing in the detection scheme shortens the recovery time to equilibrium, which is explained by a quasiparticle pumping mechanism. The second signature is an anomalous time dependence in the burst rate: a surge happens days or weeks after cooldown, followed by a strong suppression that persists until thermal cycling.