发表机构
Indian Institute of Science Education and Research; Harish-Chandra Research Institute; Homi Bhabha National Institute; Networked Quantum Devices Unit, Okinawa Institute of Science and Technology Graduate University; Université Paris-Saclay（印度科学教育与研究所; 哈里什-钱德拉研究所; 霍米·巴巴国立研究所; 冲绳科学技术大学院大学量子设备网络单元; 巴黎萨克雷大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究提出不确定时间方向计量学（ITDM），证明量子时间翻转辅助协议可突破渐近极限，在泡利噪声信道下达海森堡标度，且其超映射无法被常规量子电路模拟，确立不确定时间方向为量子计量学资源。
AI 中文摘要
在量子计量学中，对于有限次信道使用，自适应策略和因果叠加策略被证明比并行策略更具优势，但在渐近极限下它们的优势会消失。我们证明，具有不确定时间方向的量子操作，特别是时间翻转（TF）辅助的策略，即不确定时间方向计量学（ITDM），可以克服这种渐近等价性。利用半定规划，我们严格证明，TF辅助协议在有限次和渐近多次信道使用下，都能实现严格超过并行、自适应和因果叠加策略所能达到的最大值的量子费舍尔信息（QFI）。此外，我们确定了一类泡利噪声信道，对于这类信道，ITDM达到海森堡标度，而所有并行、自适应和因果叠加策略仍被限制在标准标度，我们将这一现象称为计量激活。有趣的是，这种激活可用于证明，量子时间翻转和转置超映射无法被任何有限次信道查询的常规量子电路或因果叠加策略模拟，从而确立不确定时间方向是量子计量学的真正资源。
英文摘要
In quantum metrology, adaptive and causal-superposition strategies are proven to be beneficial over parallel schemes for a finite number of channel uses, but their advantages disappear in the asymptotic limit. We show that quantum operations with indefinite time direction, specifically, time-flip (TF)-assisted strategies, referred to as indefinite time-directed metrology (ITDM), can overcome this asymptotic equivalence. Using semidefinite programming, we rigorously demonstrate that TF-assisted protocols can achieve quantum Fisher information (QFI) strictly exceeding the maximum value attainable by parallel, adaptive, and causal-superposition strategies, both for finite and asymptotically many channel uses. Moreover, we identify a class of Pauli noise channels for which ITDM achieves Heisenberg scaling, while all parallel, adaptive, and causal-superposition strategies remain restricted to standard scaling. We call this phenomenon as metrological activation. Interestingly, this activation can be used to exhibit that the quantum time-flip and transposition supermaps cannot be simulated by conventional quantum circuits or causal-superposition strategies using any finite number of channel queries, thereby establishing indefinite time direction as a genuine resource for quantum metrology.
Comments17 pages, 12 figures
