Kono Shingo, Pan Jiahe, Chegnizadeh Mahdi, Wang Xuxin, Youssefi Amir, Scigliuzzo Marco, Kippenberg Tobias J
Institute of Physics, Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland.
Center for Quantum Science and Engineering, EPFL, Lausanne, Switzerland.
Nat Commun. 2024 May 10;15(1):3950. doi: 10.1038/s41467-024-48230-3.
Superconducting qubits are among the most advanced candidates for achieving fault-tolerant quantum computing. Despite recent significant advancements in the qubit lifetimes, the origin of the loss mechanism for state-of-the-art qubits is still subject to investigation. Furthermore, the successful implementation of quantum error correction requires negligible correlated errors between qubits. Here, we realize long-lived superconducting transmon qubits that exhibit fluctuating lifetimes, averaging 0.2 ms and exceeding 0.4 ms - corresponding to quality factors above 5 million and 10 million, respectively. We then investigate their dominant error mechanism. By introducing novel time-resolved error measurements that are synchronized with the operation of the pulse tube cooler in a dilution refrigerator, we find that mechanical vibrations from the pulse tube induce nonequilibrium dynamics in highly coherent qubits, leading to their correlated bit-flip errors. Our findings not only deepen our understanding of the qubit error mechanisms but also provide valuable insights into potential error-mitigation strategies for achieving fault tolerance by decoupling superconducting qubits from their mechanical environments.
超导量子比特是实现容错量子计算的最先进候选者之一。尽管近期量子比特寿命有了显著进展，但最先进量子比特的损耗机制根源仍有待研究。此外，量子纠错的成功实施要求量子比特之间的相关误差可忽略不计。在此，我们实现了具有波动寿命的长寿命超导transmon量子比特，平均寿命为0.2毫秒，超过0.4毫秒——分别对应品质因数高于500万和1000万。然后我们研究了它们的主要误差机制。通过引入与稀释制冷机中脉冲管冷却器运行同步的新型时间分辨误差测量方法，我们发现脉冲管产生的机械振动在高度相干的量子比特中诱发了非平衡动力学，导致其相关的比特翻转误差。我们的发现不仅加深了我们对量子比特误差机制的理解，还为通过使超导量子比特与其机械环境解耦来实现容错的潜在误差缓解策略提供了有价值的见解。
