Cosmic-ray-induced correlated errors in superconducting qubit array

Correlated errors may devastate quantum error corrections that are necessary for the realization of fault-tolerant quantum computation. Recent experiments with superconducting qubits indicate that they can arise from quasiparticle (QP) bursts induced by cosmic-ray muons and γ-rays. Here, we use charge-parity jump and bit flip for monitoring QP bursts and two muon detectors in the dilution refrigerator for detecting muon events. We directly observe QP bursts leading to correlated errors that are induced solely by muons and separate the contributions of muons and γ-rays. We further investigate the dynamical process of QP burst and the impact of QP trapping on correlated errors and particle detection. The proposed method, which monitors multiqubit simultaneous charge-parity jumps, has high sensitivity to QP burst and may find applications for the detection of cosmic-ray particles, low-mass dark matter, and far-infrared photons.

关联误差可能会严重破坏实现容错量子计算所必需的量子纠错机制。近期针对超导量子比特（superconducting qubit）开展的实验表明，这类关联误差源于宇宙射线μ子与γ射线诱导产生的准粒子（quasiparticle, QP）爆发。本研究采用电荷宇称跳变（charge-parity jump）与位翻转（bit flip）两种方式监测准粒子爆发，并在稀释制冷机中部署两台μ子探测器以探测μ子事件。我们直接观测到了仅由μ子诱导产生、可引发关联误差的准粒子爆发，并区分了μ子与γ射线各自的贡献。我们还进一步研究了准粒子爆发的动力学过程，以及准粒子俘获效应对关联误差与粒子探测的影响。本研究提出的方法通过监测多量子比特同步电荷宇称跳变，对准粒子爆发具有极高的探测灵敏度，有望应用于宇宙射线粒子、低质量暗物质（low-mass dark matter）以及远红外光子（far-infrared photon）的探测领域。