2016/04/27 by Shilin Ng, Shan Zheng Ang, Trevor A. Wheatley +4 · 1 voice
Physics and Astronomy · Computer Science · #Mechanical and Optical Resonators #Quantum Information and Cryptography #Atomic and Subatomic Physics Research
paper · pdf · doi:10.1103/physreva.93.042121
openalex publication_date 2016/04/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
Measuring the power spectral density of a stochastic process, such as a stochastic force or magnetic field, is a fundamental task in many sensing applications. Quantum noise is becoming a major limiting factor to such a task in future technology, especially in optomechanics for temperature, stochastic gravitational wave, and decoherence measurements. Motivated by this concern, here we prove a measurement-independent quantum limit to the accuracy of estimating the spectrum parameters of a classical stochastic process coupled to a quantum dynamical system. We demonstrate our results by analyzing the data from a continuous-optical-phase-estimation experiment and showing that the experimental performance with homodyne detection is close to the quantum limit. We further propose a spectral photon-counting method that can attain quantum-optimal performance for weak modulation and a coherent-state input, with an error scaling superior to that of homodyne detection at low signal-to-noise ratios.