Quantum error correction (QEC) provides a practical path to fault-tolerant quantum computing through scaling to large qubit numbers, assuming that physical errors are sufficiently uncorrelated in time and space. In superconducting qubit arrays, high-energy impact events can produce correlated errors, violating this key assumption. Following such an event, phonons with energy above the superconducting gap propagate throughout the device substrate, which in turn generate a temporary surge in quasiparticle (QP) density throughout the array. When these QPs tunnel across the qubits’ Josephson junctions, they induce correlated errors. Engineering different superconducting gaps across the qubit’s Josephson junctions provides a method to resist this form of QP tunneling. By fabricating all-aluminum transmon qubits with both strong and weak gap engineering on the same substrate, we observe starkly different responses during high-energy impact events. Strongly gap engineered qubits do not show any degradation in T1 during impact events, while weakly gap engineered qubits show events of correlated degradation in T1. We also show that strongly gap engineered qubits are robust to QP poisoning from increasing optical illumination intensity, whereas weakly gap engineered qubits display rapid degradation in coherence. Based on these results, gap engineering mitigates the threat of high-energy impacts to QEC in superconducting qubit arrays. Published by the American Physical Society 2024

中文翻译：

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通过超导量子比特阵列中的间隙工程抵抗高能冲击事件


量子纠错 （QEC） 通过扩展到大量子比特数，假设物理误差在时间和空间上足够不相关，从而为容错量子计算提供了一条实用的途径。在超导量子比特阵列中，高能撞击事件会产生相关误差，这违反了这一关键假设。在此类事件之后，能量高于超导间隙的声子在整个器件衬底中传播，这反过来又在整个阵列中产生准粒子 （QP） 密度的临时浪涌。当这些 QP 穿过量子比特的 Josephson 结时，它们会引发相关误差。在量子比特的 Josephson 结上设计不同的超导间隙提供了一种抵抗这种形式的 QP 隧穿的方法。通过在同一衬底上制造具有强间隙和弱间隙工程的全铝 transmon 量子比特，我们在高能撞击事件中观察到截然不同的响应。强间隙工程量子比特在撞击事件期间不显示 T1 中的任何降解，而弱间隙工程量子比特在 T1 中显示相关降解事件。我们还表明，强间隙工程量子比特对增加光学照明强度引起的 QP 中毒具有鲁棒性，而弱间隙工程量子比特则表现出相干性的快速退化。基于这些结果，间隙工程减轻了超导量子比特阵列中高能冲击对 QEC 的威胁。 美国物理学会 2024 年出版