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Abstract |
Quantum metrology exploits quantum mechanical laws to improve the precision in estimating technologically relevant parameters such as phase, frequency, or magnetic fields. Probe states are usually tailored on the particular dynamics whose parameters are being estimated. I introduce the interferometric power of a bipartite quantum state as a figure of merit which quantifies the precision, measured by quantum Fisher information, that such a state enables for the estimation of a parameter embedded in a unitary dynamics applied to one subsystem only, in the worst-case scenario where a full knowledge of the generator of the dynamics is not available a priori. This quantity is proven to be a faithful and computable measure of quantum correlations beyond entanglement, both for finite-dimensional and infinite-dimensional systems. Quantum correlations of the ``discord'' type are thus identified as resources equivalent to coherence in all local bases. I discuss qualitative and quantitative results both for qubit-based phase estimation, and for optical interferometry with Gaussian probes. I investigate theoretically and experimentally the power of general quantum correlations even under high levels of noise, assessing their potential for real-world quantum technology.
References:
- D. Girolami et al., Phys. Rev. Lett. 112, 210401 (2014).
- G. Adesso, Phys. Rev. A 90, 022321 (2014). |
