Nico-Katz Alexander, Keenan Nathan, Goold John
School of Physics, Trinity College Dublin, Dublin 2, Ireland.
Trinity Quantum Alliance, Unit 16, Trinity Technology and Enterprise Centre, Dublin 2, Ireland.
npj Quantum Inf. 2024;10(1):124. doi: 10.1038/s41534-024-00918-6. Epub 2024 Nov 26.
Quantum computing platforms are subject to contradictory engineering requirements: qubits must be protected from mutual interactions when idling ('doing nothing'), and strongly interacting when in operation. If idling qubits are not sufficiently protected, information 'leaks' into neighbouring qubits, becoming ultimately inaccessible. Candidate solutions to this dilemma include many-body localization, dynamical decoupling, and active error correction. However, no protocol exists to quantify this effect in a similar way to e.g. SPAM errors. We develop a scalable, device non-specific, protocol for quantifying idle information loss by exploiting tools from quantum information theory. We implement this protocol in over 3500 experiments carried out across 4 months (Dec 2023-Mar 2024) on IBM's entire Falcon 5.11 processor series. After accounting for other error sources, we detect information loss to high degrees of statistical significance. This work thus provides a firm quantitative foundation from which the protection-operation dilemma can be investigated and ultimately resolved.
量子比特在闲置（“什么都不做”）时必须免受相互作用的影响，而在运行时则要强烈相互作用。如果闲置的量子比特没有得到充分保护，信息就会“泄漏”到相邻的量子比特中，最终变得无法访问。解决这一困境的候选方案包括多体局域化、动态解耦和主动纠错。然而，目前还没有一种协议能以类似于例如SPAM错误的方式来量化这种效应。我们利用量子信息理论的工具，开发了一种可扩展的、与设备无关的协议，用于量化闲置信息损失。我们在2023年12月至2024年3月的4个月里，在IBM的整个Falcon 5.11处理器系列上进行了超过3500次实验，实施了该协议。在考虑了其他误差源之后，我们检测到信息损失具有高度的统计显著性。因此，这项工作提供了一个坚实的定量基础，从中可以研究并最终解决保护 - 操作困境。
