1] Centre for Quantum Dynamics and Centre for Quantum Computation and Communication Technology, Griffith University, Brisbane, 4111, Australia [2] Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, China.
Sci Rep. 2013 Sep 25;3:2684. doi: 10.1038/srep02684.
Quantum entanglement can help to increase the precision of optical phase measurements beyond the shot noise limit (SNL) to the ultimate Heisenberg limit. However, the N-photon parity measurements required to achieve this optimal sensitivity are extremely difficult to realize with current photon detection technologies, requiring high-fidelity resolution of N + 1 different photon distributions between the output ports. Recent experimental demonstrations of precision beyond the SNL have therefore used only one or two photon-number detection patterns instead of parity measurements. Here we investigate the achievable phase sensitivity of the simple and efficient single interference fringe detection technique. We show that the maximally-entangled "NOON" state does not achieve optimal phase sensitivity when N > 4, rather, we show that the Holland-Burnett state is optimal. We experimentally demonstrate this enhanced sensitivity using a single photon-counted fringe of the six-photon Holland-Burnett state. Specifically, our single-fringe six-photon measurement achieves a phase variance three times below the SNL.
量子纠缠可以帮助将光学相位测量的精度提高到超越散粒噪声极限（SNL），达到最终的海森堡极限。然而，要实现这种最佳灵敏度，需要进行 N 光子奇偶性测量，这在当前的光子检测技术中极其难以实现，需要高精度地分辨 N+1 种不同的光子分布在输出端口之间。最近超越 SNL 的实验演示因此仅使用了一个或两个光子数检测模式，而不是奇偶性测量。在这里，我们研究了简单高效的单干涉条纹检测技术的可实现相位灵敏度。我们表明，当 N > 4 时，最大纠缠的“NOON”状态并不能实现最佳的相位灵敏度，相反，我们表明 Holland-Burnett 态是最佳的。我们使用六光子 Holland-Burnett 态的单光子计数条纹实验证明了这种增强的灵敏度。具体来说，我们的单条纹六光子测量实现了相位方差低于 SNL 三倍的结果。
