恒定深度的全局阴影估计
Constant-depth global shadow estimation
- Fudan University（复旦大学）
- Peking University（北京大学）
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), and Department of Physics, Fudan University（复旦大学表面物理国家重点实验室、微纳光子结构教育部重点实验室和物理系）
- Shanghai Qi Zhi Institute（上海人工智能实验室（智源研究院））
- Institute of Nanoelectronics and Quantum Computing, Fudan University（复旦大学纳米电子与量子计算研究所）
- Shanghai Artificial Intelligence Laboratory（上海人工智能实验室）
- Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）
- Freie Universität Berlin（柏林自由大学）
- Helmholtz-Zentrum Berlin für Materialien und Energie（亥姆霍兹柏林材料能源中心）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究提出浅层相位阴影协议，利用稀疏Clifford-IQP系综实现恒定深度的全局稳定子态保真度估计，减少随机性需求，适用于长程连接架构。
AI中文摘要：
可靠且可扩展的读出策略对于量子技术至关重要。随着量子处理器规模的增大，在不使测量电路成为主要瓶颈的情况下提取有用信息必须保持可行性。随机测量和经典阴影提供了一条强大的途径，但全局估计通常与高度随机的系综相关联，这需要增加电路深度，从而带来大量的实验开销。在这项工作中，我们表明，当读出针对被估计的量进行有意义的调整时，所需的随机性可以大幅减少。我们引入了基于稀疏Clifford-IQP系综的浅层相位阴影，并证明了即使该系综不构成近似相对误差设计，也能高效地估计稳定子态的保真度。在全连接架构上，该协议允许使用中间电路测量和经典前馈实现恒定深度，或者在没有辅助系统的情况下实现对数深度。该协议仅需要受控相位纠缠门，并提供电路资源与估计精度之间的可调权衡，使其特别适用于具有长程连接性的实验相关架构。我们的结果表明，可扩展的量子读出不需要再现通用随机性：任务自适应的随机化可以实现更浅的全局表征协议。
英文摘要：
Reliable and scalable readout strategies are essential for quantum technologies. As quantum processors grow, extracting useful information must remain feasible without measurement circuits becoming a dominant bottleneck. Randomized measurements and classical shadows provide a powerful route, but global estimation is conventionally associated with highly random ensembles that require increasing circuit depth and hence substantial experimental overhead. In this work, we show that substantially less randomness suffices when the readout is meaningfully adapted to the quantities being estimated. We introduce shallow phase shadows, based on a sparse Clifford-IQP ensemble, and prove efficient global estimation of stabilizer-state fidelities despite the ensemble not forming an approximate relative-error design. On all-to-all architectures, the protocol admits a constant-depth implementation using mid-circuit measurements and classical feedforward, or logarithmic depth without auxiliary systems. The protocol requires only controlled-phase entangling gates and offers a tunable trade-off between circuit resources and estimation accuracy, making it particularly amenable to experimentally relevant architectures with long-range connectivity. Our results show that scalable quantum readout need not reproduce generic randomness: task-adapted randomization can enable substantially shallower global characterization protocols.
