The Noise Mechanism In Quantum Metrology

Quantum metrology pursues the physical realization of higher-precision measurement to physical quantities than the classically achievable limits by exploiting quantum characters as resources.Due to its revolutionary innovation to the nowadays techniques of weak magnetic-field detection,optical imaging resolution,and highly sensitive displacement measurement,quamtum metrology opens a new door from the fundamental rules of quantum mechanics to develop next-generation quantum magnetometer,radar,and global positioning systems.The widely used quantum metrology schemes are based on either the Ramsey interferometer using entangled two-level atoms as probe or the Mach-Zehnder interferometer using squeezed light as probe.However,the ubiquitous decoherence of the atom and the quantized light degrades the quantum resources and greatly hinders the practical application of quantum metrology.Therefore,how to realize the promised performance of quantum metrology in practical decoherence situation attracts much attention in recent years.Previous studies showed that the precisions in both of the Ramsey-interferometerbased and the Mach-Zehnder-interferometer-based quantum metrology schemes return to the shot noise limit governed by classical physics when the decoherence of the quantum probes occurs.However,they were based on either phenomenological or BornMarkovian approximate descriptions to the decoherence.Going beyond these methods,we here develop a microscopic method and propose a mechanism to make the promised precisions in ideal scheme asymptotically recovered when the exact non-Markovian decoherence of the entangled atoms and the squeezed light is seriously considered.Our analysis reveals that it is due to the formation of a bound state between each quantum probes and their local dissipative noises.On the one hand,our result highlights the microscopic mechanism of the dissipative noise on the quantum metrology and enriches our understanding to the decoherence effect on the quantum metrology,and on the other hand it supplies an experimentally accessible way to realize ultrasensitive measurement in practice.With the mechanism to restore the ideal precision revealed in our work,people are readily to engineer the formation of the bound state via the rapidly developing quantum reservoir engineering technique to realize ultra-highly precisive metrology in the realistic situation.Therefore,our result expectedly supplies an insightful instruction for experiment to implement quantum metrology in practical decoherence situation.