Operational Resource Theory of Nonclassicality via Quantum Metrology

Abstract

The nonclassical properties of quantum states are of tremendous interest due to their potential applications in future technologies. It has recently been realized that the concept of a "resource theory" is a powerful approach to quantifying and understanding nonclassicality. To realize the potential of this approach one must first find resource theoretic measures of nonclassicality that are "operational", meaning that they also quantify the ability of quantum states to provide enhanced performance for specific tasks, such as precision sensing. Here we achieve a significant milestone in this endeavor by presenting the first such operational resource theoretic measure. In addition to satisfying the requirements of a resource measure, it has the closest possible relationship to the quantum-enhancement provided by a non-classical state for measuring phase-space displacement: it is equal to this enhancement for pure states, and is a tight upper bound on it for mixed states. We also show that a lower-bound on this measure can be obtained experimentally using a simple Mach-Zehnder interferometer.

8 pages, 1 figure, Updated

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• Optimal entanglement enhancing via conditional measurements
• Beam splitter as quantum coherence-maker
• Multicopy observables for the detection of optically nonclassical states
• Classes of Gaussian States for Squeezing Estimation
• Coherence behavior of strongly coupled bosonic modes
• An introductory review on resource theories of generalized nonclassical light
• Fundamental limits on concentrating and preserving tensorized quantum resources
• Entanglement, loss, and quantumness: When balanced beam splitters are best
• Filter functions for the Glauber-Sudarshan $P$-function regularization
• Nonclassical photocounting statistics with a single on-off detector