Estimation of the properties of a physical system with minimal uncertainty is a central task in quantum metrology. Optical phase estimation is at the center of many metrological tasks where the value of a physical parameter is mapped to the phase of an electromagnetic field and single-shot measurements of this phase are necessary. While there are measurements able to estimate the phase of light in a single shot with small uncertainties, demonstrations of near-optimal single-shot measurements for an unknown phase of a coherent state remain elusive. Here, we propose and demonstrate strategies for single-shot measurements for ab initio phase estimation of coherent states that surpass the sensitivity limit of heterodyne measurement and approach the Cramer-Rao lower bound for coherent states. These single-shot estimation strategies are based on real-time optimization of coherent displacement operations, single photon counting with photon number resolution, and fast feedback. We show that our demonstration of these optimized estimation strategies surpasses the heterodyne limit for a wide range of optical powers without correcting for detection efficiency with a moderate number of adaptive measurement steps. This is, to our knowledge, the most sensitive single-shot measurement of an unknown phase encoded in optical coherent states.

中文翻译：

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用于光学相位估计的单次非高斯测量

估计具有最小不确定性的物理系统的属性是量子计量学的核心任务。光学相位估计是许多计量任务的中心，在这些任务中，物理参数的值映射到电磁场的相位，因此必须对该相位进行单次测量。尽管有一些测量方法可以在不确定性很小的情况下估计单发光的相位，但是对于相干态未知相位的近乎最佳单发测量的演示仍然难以捉摸。在这里，我们提出并演示了从头算起单次测量的策略相干态的相位估计超过外差测量的灵敏度极限，并达到相干态的Cramer-Rao下界。这些单发估计策略基于相干位移操作的实时优化，具有光子数量分辨率的单光子计数以及快速反馈。我们展示了我们对这些优化估计策略的论证，在不使用中等数量的自适应测量步骤来校正检测效率的情况下，超出了大范围光功率的外差极限。据我们所知，这是对以光学相干态编码的未知相位的最灵敏的单次测量。