Quantum-enhanced Metrology with hundreds of Photons

Utilizing photons in a harmonic oscillator for small signal detection is a promising method to realize hardware-efficient quantum-enhanced metrology. However, manipulating and detecting a large number of photons remains challenging in experiment. In this work, we experimentally demonstrate a new scheme that leveraging the photon number compression state with hundreds of photons to realize quantum enhanced sensitivity in displacement signal detection. Inspired by the optical method, we design a deterministic quantum circuit that realize efficiently preparation and precise detection of the photon number compression state. By utilizing hundreds of photons in a high-coherence superconducting cavity, we achieve a displacement signal detection sensitivity far surpassing the standard quantum limit. Our result establishes a scalable and efficient pathway toward practical implementations of quantum-enhanced metrology.