Experimental Demonstration of Quantum Metrology using Continuous-Wave Laser

利用中午态和光子数分辨探测器，用马赫-曾德尔干涉仪测量相位的精度达到了海森堡极限。在使用连续波正午状态的实验演示中，相干时间比光子数分辨探测器的响应时间长得多。因此，我们利用马赫-曾德尔干涉仪研究了光场中光子探测事件的时间相关性。结果发现，光子探测事件是反聚束的。这一结果表明，我们需要一个响应时间快的光子数分辨探测器和一个相干时间长得多的正午状态，才能使用大光子数正午状态。

Using the NOON state and a photon-number-resolving detector, the accuracy of phase measurement with a Mach–Zehnder interferometer reached the Heisenberg limit. In an experimental demonstration using the continuous-wave NOON state, the coherence time was much longer than the response time of a photon-number-resolving detector. Therefore, we investigated the time correlation of photon detection events in the light field from the Mach–Zehnder interferometer. As a result, it was found that the photon detection events were anti-bunching. This result suggests that we need a photon-number-resolving detector with a fast response time and a NOON state with a much longer coherence time in order to use a large-photon-number NOON state.