发表机构
Technion University; The Helen Diller Quantum Center; MIGAL – Galilee Research Institute; Tel-Hai University of Kiryat Shmona and the Galilee（以色列理工学院; 海伦·迪勒量子中心; 米加尔-加利利研究所; 基里亚特谢莫纳和加利利泰尔海大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究采用“什么都不做”态转移协议对比评估Rigetti Cepheus-1-108Q与IBM Heron-r2量子处理器，揭示二者在均匀空间可靠性与最佳路由性能上的显著差异。
AI 中文摘要
我们采用成熟的“什么都不做”态转移协议，对Rigetti的Cepheus-1-108Q和IBM Heron-r2处理器开展了按路由划分的对比评估。我们并未提出新协议，而是将这种确定性、低复杂度的任务用作高分辨率空间探针。针对每个被评估的初始量子比特，我们报告两个互补量：所有被评估最短路由均满足操作成功规则的最大测试半径，以及在被评估路由族中识别出的最长成功路由。为实现这一目标，我们探讨了一个看似简单却具有基础性的问题：“在量子计算机上，你能‘什么都不做’到什么程度？”从操作层面看，这种“什么都不做”协议是一种基础态转移协议：我们制备初始量子态，通过SWAP门将其在物理量子比特间路由，并将最终态保真度与成熟的单量子比特态转移经典保真度极限进行比对。尽管这种简单的态转移协议是最直观的基准，但在物理晶格上主动保持量子态是一项非平凡任务，会使量子信息面临累积弛豫、退相和环境串扰的影响。在重点研究的IBM QPU案例中，我们确定其各向同性半径为10，且存在一条SWAP距离为27的成功路径；而重点研究的Rigetti Cepheus案例的各向同性半径为1，但存在部分超过阈值的路由达到SWAP距离8。这些结果揭示了均匀空间可靠性与最佳路由性能之间的显著差异。所报告的量是经验性的，且取决于被评估的路由族、有限次测量的决策规则、校准态和执行时间；它们并非架构范围内的常数。
英文摘要
We present a route-resolved comparative assessment of Rigetti's Cepheus-1-108Q and IBM Heron-r2 processors using the established do-nothing state-transfer protocol. Rather than proposing a new protocol, we use this deterministic, low-complexity task as a high-resolution spatial probe. For each evaluated initial qubit, we report two complementary quantities: the largest tested radius within which every evaluated shortest route satisfies the operational success rule, and the longest successful route identified within the evaluated route family. To address the question "How far can you do-nothing on a quantum computer?", we prepare a quantum state, route it outward using SWAP gates, apply the inverse preparation at the destination, and route it back for measurement. We compare the measured probability of returning $0$ with the empirical cutoff $2/3$. For this circuit ordering, that comparison does not certify above-classical unknown-state transfer. While this trivial state-transfer protocol serves as the most intuitive baseline, actively preserving a quantum state across a physical lattice proves to be a non-trivial task that exposes the information to cumulative relaxation, dephasing, and environmental cross-talk. In the highlighted IBM QPU case, we identify an isotropic radius of 10 and a successful path of swap distance 27, whereas the highlighted Rigetti Cepheus case exhibits an isotropic radius of 1 but selected above-threshold routes reaching swap distance 8. These results reveal a sharp distinction between uniform spatial reliability and best-route performance. The presented quantities are empirical and conditional on the evaluated route families, finite-shot decision rule, calibration state, and execution time; they are not architecture-wide constants.
Comments57 pages, including supplementary material. Revised figures and expanded supplementary maps; clarified the return-score interpretation and methodological limitations
