Quantum Data Ruler

Abstract:A ruler reads an unknown length against a calibrated scale. The quantum data ruler reads a matrix element of an unknown state against the signal of a known reference, from their ratio. It is exact for any Hamiltonian and any time, since transition operators change by a state-dependent constant times one function of time, removing the vanishing-signal limit. The readout is unbiased under dephasing and amplitude damping, and recovers the coherent ergotropy of a quantum battery that two-point measurement erases. The structure survives the classical limit as action--angle Fourier modes.

arXiv:2610.07827 [quant-ph]

(or arXiv:2610.07827v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2610.07827 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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