Quantum-enhanced metrology with large Fock states

Quantum metrology uses non-classical states, such as Fock states with a specific number of photons, to achieve an advantage over classical sensing methods. Typically, quantum metrological performance can be enhanced by increasing the involved excitation numbers, for example, by using large-photon-number Fock states. However, manipulating these states and demonstrating a quantum metrological advantage is experimentally challenging. Here we present an efficient method for generating large Fock states approaching 100 photons within a superconducting microwave cavity through the development of a programmable photon number filter. Using these states in displacement and phase measurements, we demonstrate quantum-enhanced metrology approaching the Heisenberg scaling for 40-photon Fock states and achieve a maximum metrological gain of up to 14.8 dB, highlighting the metrological advantages of large Fock states. Our study could be readily extended to mechanical and optical systems, promising potential applications in weak force detection and dark matter searches.

Xiaowei Deng, Sai Li, Zi-Jie Chen, Zhongchu Ni, Yanyan Cai, Jiasheng Mai, Libo Zhang, Pan Zheng, Haifeng Yu, Chang-Ling Zou, Song Liu, Fei Yan, Yuan Xu, Dapeng Yu