发表机构
Tel Aviv University（特拉维夫大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文在可编程硬件上首次认证测量并控制了量子信道的纠缠破坏指数，通过热碰撞反馈回路实现整数阶梯的测量与脉冲式控制，并给出区间算术证书。
AI 中文摘要
量子信道的纠缠破坏指数，即信道在自复合若干次后破坏与任何参考系的所有纠缠的次数，据我们所知从未被测量过。我们证明，一个经过认证的热碰撞反馈回路使得该整数在当前可编程硬件上既可测量又可控制，所有承重量均以区间算术证书的形式交付。在测量方面：针对整数阶梯 n_EB(p) 的目标列表，其决策点负性以 0.025 至 0.109 的余量得到认证；一个精确的逐轮退极化模型，其中所选阶梯在现实噪声下以认证整数形式存活；对轮次酉变换的精确且紧凑的编译（七个全连接 CNOT，五个原生任意角度门，十个在重六边形上）；以及一次 3300 万次抽取的门控搜索，将热谷的对比度限制为具有内部最大值的壁，在接近 89 层处获得认证的 2.85×10^-3。在控制方面：该模型精确地组合不同浴极化的轮次，因此谷变成脉冲阀，在恰好八轮的认证最小脉冲下切换；最优脉冲信号（认证为 3.43×10^-3）优于静态协议，因此最佳谷测量本质上是脉冲式的；浴 Bloch 矢量的相干倾斜将信号提升至认证的 8.6×10^-3，是静态上限的三倍，且零布居成本。谷特征在每轮噪声强度约 10^-4 时被认证地消亡，从而确定了误差外推负担。阶梯是近期实验；脉冲谷则是精确定价的实验。
英文摘要
The entanglement-breaking index of a quantum channel is the smallest number of self-compositions after which the channel destroys all entanglement with any reference system. A photonic experiment has fixed an index of 2; to our knowledge no larger index has been located by measuring the n-round channel across rounds. We give a protocol for doing so on a programmable processor, for any qubit channel realised as a collision model whose ancillas are prepared in states diagonal in a known basis, so that the bath polarisation is set exactly by weighting basis-state configurations in the analysis. Single-qubit process tomography of the n-round channel gives the smallest eigenvalue of its partially transposed Choi matrix, read against zero at a pre-registered five standard deviations; entanglement breaking survives further rounds, so the readings are monotone in n and the index follows. Comparing each direct measurement with the composition of the measured single-round map tests the repeated-interaction assumption. We show that a readable step needs margins on both sides, show how depolarising and reset errors move the readings, and give a power-based pilot rule. As a worked example we take one round of a three-qubit feedback loop, compiled to eight CZ gates on a heavy-hex path with mid-circuit reset, with certified ideal indices 3, 2 and 2 for three baths. The run is estimated to cost a few hundred seconds of processor time, and simulations under a device noise model, with the pilot's shot raise at low noise, recover all three indices.
Comments19 pages, 2 figures, 5 tables. v3: rewritten as a measurement protocol with a worked example (compilation, budget, simulated runs under a device noise model); corrects several statements of v2; all v2 ancillary files kept, protocol code and simulation records added in anc/staircase
