Real-time detection of correlated quasiparticle tunneling events in a multi-qubit superconducting device

TL;DR

This paper presents a method for real-time detection and analysis of quasiparticle tunneling events in superconducting qubits, revealing their correlation patterns and potential for error mitigation in quantum computing.

Contribution

The study introduces a practical technique for detecting quasiparticle bursts and analyzing their correlations in multi-qubit superconducting devices.

Findings

Quasiparticle tunneling rates are measured at the single-hertz level.

Burst episodes occur about once per minute and are largely correlated across devices.

A rare subset of bursts is associated with shifts in offset charge.

Abstract

Quasiparticle tunneling events are a source of decoherence and correlated errors in superconducting circuits. Understanding and ultimately mitigating these errors calls for real-time detection of quasiparticle tunneling events on individual devices. In this work, we simultaneously detect quasiparticle tunneling events in two co-housed, charge-sensitive transmons coupled to a common waveguide. We measure background quasiparticle tunneling rates at the single-hertz level, with temporal resolution of tens of microseconds. Using time-tagged coincidence analysis, we show that individual events are uncorrelated across devices, whereas burst episodes occur about once per minute and are largely correlated. These bursts have a characteristic lifetime of 7 ms and induce a thousand-fold increase in the quasiparticle tunneling rate across both devices. In addition, we identify a rarer subset of bursts which are accompanied by a shift in the offset charge, at approximately one event per hour. Our results establish a practical and extensible method to identify quasiparticle bursts in superconducting circuits, as well as their correlations and spatial structure, advancing routes to suppress correlated errors in superconducting quantum processors.