Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China; CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; and Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China.
Phys Rev Lett. 2023 Feb 17;130(7):070801. doi: 10.1103/PhysRevLett.130.070801.
Quantum metrology employs quantum resources to enhance the measurement sensitivity beyond that can be achieved classically. While multiphoton entangled N00N states can in principle beat the shot-noise limit and reach the Heisenberg limit, high N00N states are difficult to prepare and fragile to photon loss which hinders them from reaching unconditional quantum metrological advantages. Here, we combine the idea of unconventional nonlinear interferometers and stimulated emission of squeezed light, previously developed for the photonic quantum computer Jiuzhang, to propose and realize a new scheme that achieves a scalable, unconditional, and robust quantum metrological advantage. We observe a 5.8(1)-fold enhancement above the shot-noise limit in the Fisher information extracted per photon, without discounting for photon loss and imperfections, which outperforms ideal 5-N00N states. The Heisenberg-limited scaling, the robustness to external photon loss, and the ease-of-use of our method make it applicable in practical quantum metrology at a low photon flux regime.
量子计量学利用量子资源来提高测量灵敏度，超越经典方法所能达到的水平。虽然多光子纠缠 N00N 态原则上可以打破散粒噪声限制并达到海森堡极限，但高 N00N 态很难制备，而且对光子损失很脆弱，这阻碍了它们实现无条件的量子计量优势。在这里，我们结合了非常规非线性干涉仪和压缩光受激发射的思想，这些思想之前是为光子量子计算机“九章”开发的，提出并实现了一种新方案，实现了可扩展、无条件和稳健的量子计量优势。我们观察到每光子提取的 Fisher 信息超过散粒噪声限制 5.8(1)倍，没有考虑光子损失和不完美，这超过了理想的 5-N00N 态。我们方法的海森堡极限缩放、对外部光子损失的鲁棒性以及易用性使其适用于低光子通量下的实际量子计量学。
