A novel high-precision refractive index measurement scheme based on entangled coherent states and parity detectionOA

Traditional intensity-based refractive index measurement methods are constrained by the classical diffraction limit and the shot noise limit,which severely restricts the improvement of measurement precision.To address this issue,a novel quantum measurement scheme integrating entangled coherent states(ECS)and parity detection(PD)is proposed.Taking advantage of the non-classical correlation of quantum entanglement,the scheme constructs a dual-mode entangled coherent state light source and realizes high-fidelity signal demodulation through a customized parity detection system.Theoretical derivation and numerical simulation results demonstrate that the measurement resolution of the proposed scheme breaks through the Rayleigh limit,achieving a■-fold improvement compared with the traditional coherent state measurement method in the full loss range.In lossless scenarios and cases with loss rates below 10%,the sensitivity surpasses the shot noise limit.Finally,the experimental challenges are also elaborated in detail.This quantum measurement architecture provides a new technical pathway for precision optical detection,biosensing,and other fields,exhibiting significant practical value and broad application prospects.