发表机构
CUNEF Universidad（CUNEF大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
在九量子比特超导处理器上，通过修正QAOA代价层，认证了二分纠缠，并因果验证了CZ脉冲幅度对纠缠的控制，但深度三时无优化优势。
AI 中文摘要
量子近似优化算法（QAOA）是典型的近期启发式算法，然而在真实的超导硬件上，其行为由器件物理决定，而非算法本身。硬件演示很少证明预期的耦合已实现、真正的纠缠已制备，或什么因素控制着纠缠。我们报告了一项在巴塞罗那超算中心的九量子比特超导处理器Red上进行的预注册单设备研究，使用其五量子比特组件。在六次校准中，我们通过两量子比特层析负性认证了深度一的好耦合器上修正的QAOA代价层的二分纠缠：负性值为0.077，偏差校正加速（BCa）95%置信区间为[0.065, 0.091]，每天均排除零，而耦合关闭的孪生设备保持可分离，退化耦合器的负性等于零。随后我们直接测量器件物理：在预注册的固定贝尔态制备（非QAOA层）操作中，降低CZ脉冲幅度因果性地降低了认证负性，沿正向拟合斜率（R² = 0.83-0.96），每一梯级区间均排除零，并通过Holm和Benjamini-Hochberg校正。这是峰值响应的局部线性化，而非全局单调规律：负性在条件相位|ζ| = π处达到峰值，而标称幅度超调了该值。J=0孪生设备是独立的关闭态控制，条纹可见度恒定，因此该效应是相干的。平均门保真度随驱动非单调变化，仅作为诊断报告。每电路态矢量护栏排除了我们披露并修复的对角编译故障。随机测量见证与纠缠一致但功效不足。证书在深度三时失效，预注册的十六实例深度三集成显示无优化信号（单侧Wilcoxon p = 0.15）。我们不声称优势；实例在经典上平凡。
英文摘要
The Quantum Approximate Optimisation Algorithm is the canonical near-term heuristic, yet on real superconducting hardware its behaviour is set by device physics, not by the algorithm. Hardware demonstrations rarely prove the intended coupling is realised, that genuine entanglement is prepared, or what controls it. We report a pre-registered single-device study on the nine-qubit superconducting processor Red at the Barcelona Supercomputing Center, using its five-qubit component. Across six calibrations we certify bipartite entanglement of a corrected QAOA cost layer on the good coupler at depth one by two-qubit tomographic negativity: 0.077, BCa 95% CI [0.065, 0.091], excluding zero every day, while the coupling-off twin stays separable and the degraded coupler equals zero. We then measure the device physics directly: in a pre-registered manipulation on a fixed Bell preparation (not the QAOA layer), reducing the CZ pulse amplitude causally reduces the certified negativity along a positive, well-fit slope (R^2 = 0.83-0.96), every rung-level interval excluding zero and surviving Holm and Benjamini-Hochberg correction. This is a local linearisation of a peaked response, not a global monotone law: the negativity peaks at conditional phase |zeta| = pi, which the nominal amplitude overshoots. The J=0 twin is a separate off-state control and the fringe visibility is constant, so the effect is coherent. The average gate fidelity is non-monotone in the drive and is reported only as a diagnostic. A per-circuit statevector guardrail excludes a diagonal compilation fault we disclose and repair. A randomized-measurement witness is consistent with entanglement but underpowered. The certificate collapses by depth three, and a pre-registered sixteen-instance depth-three ensemble shows no optimisation signal (one-sided Wilcoxon p = 0.15). We claim no advantage; the instances are classically trivial.
Comments28 pages, 6 figures
