2024/02/23 by Matt McEwen, Kevin C. Miao, McEwen, Matt +51 · 8 citations
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #Particle physics theoretical and experimental studies #Quantum Physics (quant-ph)
paper · pdf · doi:10.48550/arxiv.2402.15644
openalex publication_date 2024/02/23 · openalex created_date 2024/02/28 · openalex updated_date 2026/07/28
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 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 removes the threat of high-energy impacts to QEC in superconducting qubit arrays.