Resolving catastrophic error bursts from cosmic rays in large arrays of superconducting qubits

TL;DR

This paper demonstrates direct observation of cosmic ray impacts on large superconducting qubit arrays, revealing how high-energy particles induce widespread errors and emphasizing the need for mitigation strategies to enable scalable quantum computing.

Contribution

It introduces a novel rapid measurement technique to track cosmic ray events in large quantum processors, providing detailed insights into error burst dynamics and their impact on qubit coherence.

Findings

Cosmic rays cause chip-wide qubit failures through quasiparticle bursts.

The new measurement method resolves events in space and time.

Large-scale quantum devices are vulnerable to energetic particle impacts.

Abstract

Scalable quantum computing can become a reality with error correction, provided coherent qubits can be constructed in large arrays. The key premise is that physical errors can remain both small and sufficiently uncorrelated as devices scale, so that logical error rates can be exponentially suppressed. However, energetic impacts from cosmic rays and latent radioactivity violate both of these assumptions. An impinging particle ionizes the substrate, radiating high energy phonons that induce a burst of quasiparticles, destroying qubit coherence throughout the device. High-energy radiation has been identified as a source of error in pilot superconducting quantum devices, but lacking a measurement technique able to resolve a single event in detail, the effect on large scale algorithms and error correction in particular remains an open question. Elucidating the physics involved requires operating large numbers of qubits at the same rapid timescales as in error correction, exposing the event's evolution in time and spread in space. Here, we directly observe high-energy rays impacting a large-scale quantum processor. We introduce a rapid space and time-multiplexed measurement method and identify large bursts of quasiparticles that simultaneously and severely limit the energy coherence of all qubits, causing chip-wide failure. We track the events from their initial localised impact to high error rates across the chip. Our results provide direct insights into the scale and dynamics of these damaging error bursts in large-scale devices, and highlight the necessity of mitigation to enable quantum computing to scale.