发表机构
BlueQubit; Institute of Physics, École Polytechnique Fédérale de Lausanne; XPRIZE Foundation（BlueQubit; 洛桑联邦理工学院物理研究所; XPRIZE基金会）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究在IBM Nighthawk r2超导量子处理器上，通过61量子比特的随机电路采样，验证了量子计算优势，其36周期电路在保真度估计上超越经典模拟，仅需19秒即可完成经典超级计算机需超百年的采样任务。
AI 中文摘要
我们报告了在120量子比特的Nighthawk r2超导处理器（\textit{ibm\\_phoenix}）上进行的正向随机电路采样（RCS），该处理器具有方格晶格连接性，使用了61个量子比特、原生CZ门以及标准云执行栈，未进行针对基准的校准。两个独立的保真度估计器——镜像基准测试和三块及四块交叉熵基准测试（XEB）——在每一个测量的深度上彼此一致，镜像从4到40个周期，分块估计器从20到40个周期，跨越了超过两个数量级的保真度衰减，并且在固定深度上比第一代Nighthawk r1设备高出一个数量级以上。36个周期的电路处于张量网络收缩成本在系统规模上饱和的深度：一个针对已发表的Sycamore和Zuchongzhi网络验证的收缩成本估计器将单振幅成本置于约$10^{22}$次复数运算。在有利的内存假设下，$F_{\mathrm{XEB}}(36)=2.3\times10^{-3}$意味着在有界保真度拒绝采样模型内需要$1.2\times10^{27}$次机器运算——在Frontier超级计算机上运行超过一个世纪——才能收集到$10^{6}$样本的集合，而这在Nighthawk r2上仅需19秒。据我们所知，这是首次在商业且广泛可访问的量子处理器上展示普通随机电路采样的量子优势，大多数非专家量子计算机用户都能轻松复现。
英文摘要
We report forward random-circuit sampling (RCS) on the 120-qubit Nighthawk r2 superconducting processor (\textit{ibm\_phoenix}) with square-lattice connectivity, using 61 qubits, native CZ gates, and the standard cloud execution stack with no benchmark-specific calibration. Two independent fidelity estimators---mirror benchmarking and three- and four-patch cross-entropy benchmarking (XEB)---agree with each other at every measured depth, the mirror from 4 to 40 cycles and the patched estimators from 20 to 40 cycles, across more than two orders of magnitude of fidelity decay, and exceed the first-generation Nighthawk r1 device by more than an order of magnitude at fixed depth. The 36-cycle circuits sit at the depth where tensor-network contraction cost saturates at system size: a contraction-cost estimator validated against the published Sycamore and Zuchongzhi networks places the single-amplitude cost at $\sim$$10^{22}$ complex operations. At $F_{\mathrm{XEB}}(36)=2.3\times10^{-3}$ under favorable memory assumptions this implies $1.2\times10^{27}$ machine operations within the bounded-fidelity rejection-sampling model --- more than a century of runtime on the Frontier supercomputer --- to collect a $10^{6}$-sample ensemble, which takes only 19\,s on Nighthawk r2. To our knowledge, this is the first demonstration of quantum advantage for a vanilla random-circuit sampling on a commercially and broadly accessible quantum processor that most non-expert quantum computer users can easily replicate.
