Abstract
Estimation of physical parameters is essential in almost any part of science and technology. The enhancement of performance in this task (e.g. beating the standard classical shot-noise limit) using available physical resources is a major goal in metrology. Quantum metrology in closed systems has indicated that entanglement in such systems may be a useful resource. However, whether in open quantum systems such enhancements may still show up is not yet fully understood. Here, we consider a dissipative (open) quantum system of identical particles in which a parameter of the open dynamics itself is to be estimated. We employ a recently developed dissipative quantum metrology framework, and investigate whether the entanglement produced in the course of the dissipative dynamics may help the estimation task. Specifically, we show that, even in a Markovian dynamics in which states become less distinguishable in time, at small enough times the entanglement generated by the dynamics may offer some advantage over the classical shot-noise limit.
Highlights
Quantum entanglement is perhaps the most intriguing consequence of the linear structure of quantum mechanics
Since the EPR gedankenexperiment [1], the perception of the phenomenon changed from being an argument against the compatibility of quantum mechanics with special relativity to becoming a physical resource usable to perform tasks that would be impossible in a completely classical world
If a parameter α appears in a unitary transformation e−iαJ generated by a self-adjoint operator J, one can measure α by subjecting a system in an initial stateto the unitary operator e−iαJ, mapping it into e−iαJeiαJ
Summary
Quantum entanglement is perhaps the most intriguing consequence of the linear structure of quantum mechanics. Pure bosonic states must be symmetric under exchange of particles, and mixed states must be convex combinations of projections onto such states This fact necessitates a different approach to the notions of nonlocality and entanglement based not on a structure related to the particle aspect of first quantization, but rather on the behavior of correlation functions of commuting observables more generally related to the mode description typical of second quantization picture. We shall consider the dissipative time evolution of an open quantum system consisting of N two-mode bosons governed by an entanglement-generating master equation, and investigate whether the generated entanglement is useful to go beyond the shot-noise limit To this end, we need first to develop a nonunitary framework for the QFI and related techniques
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