Distinguishing types of correlated errors in superconducting qubits

TL;DR

This paper introduces a method to distinguish and analyze correlated errors in superconducting qubits caused by radiation and vibrations, aiding in developing targeted error mitigation strategies.

Contribution

The authors present a novel approach to differentiate between radiation- and vibration-induced errors in superconducting qubits using their temporal, spatial, and frequency characteristics.

Findings

Devices with larger superconducting gap differences are protected against both radiation and vibration errors.

The method effectively identifies the source of correlated errors in qubit arrays.

Vibration mitigation correlates with reduced error rates in specific qubit configurations.

Abstract

Errors in superconducting qubits that are correlated in time and space can pose problems for quantum error correction codes. Radiation from cosmic and terrestrial sources can increase the quasiparticle (QP) density in a superconducting qubit device, resulting in an increased rate of QPs tunneling across proximal Josephson junctions (JJs) and causing correlated errors. Mechanical vibrations, such as those induced by the pulse tube in a dry dilution refrigerator, are also a known source of correlated errors. We present a method for distinguishing these two types of errors by their temporal, spatial, and frequency domain features, enabling physically motivated error-mitigation strategies. We also present accelerometer data to study the correlation between dilution refrigerator vibrations and the errors. We measure arrays of transmon qubits where the difference in superconducting gap across the JJ is less than the qubit energy, as well as those where the gap is greater than the qubit energy, which has been shown to mitigate radiation-induced errors. We show that these latter devices are also protected against vibration-induced errors.