Disentangling the sources of ionizing radiation in superconducting qubits

TL;DR

This paper investigates the sources of ionizing radiation affecting superconducting qubits, quantifies their impact, and proposes mitigation strategies to improve qubit coherence in low-radioactivity environments.

Contribution

It provides a comprehensive measurement and simulation of radioactivity sources in typical lab environments and materials used for superconducting qubits, along with mitigation proposals.

Findings

Radioactive isotopes contribute to qubit decoherence.

Simulations predict impact rates and energy depositions.

Mitigation strategies can reduce radiation-induced errors.

Abstract

Radioactivity was recently discovered as a source of decoherence and correlated errors for the real-world implementation of superconducting quantum processors. In this work, we measure levels of radioactivity present in a typical laboratory environment (from muons, neutrons, and gamma's emitted by naturally occurring radioactive isotopes) and in the most commonly used materials for the assembly and operation of state-of-the-art superconducting qubits. We develop a GEANT-4 based simulation to predict the rate of impacts and the amount of energy released in a qubit chip from each of the mentioned sources. We finally propose mitigation strategies for the operation of next-generation qubits in a radio-pure environment.