A Fundamental Upper Bound for Signal to Noise Ratio of Quantum Detectors

TL;DR

This paper establishes a fundamental upper limit on the signal-to-noise ratio in quantum detectors, based on quantum fidelity, regardless of the specific observables measured, highlighting intrinsic quantum noise constraints.

Contribution

It introduces a universal upper bound on quantum detection signal-to-noise ratio derived from quantum fidelity, applicable to any quantum detection scenario with trace-class operators.

Findings

The upper bound is independent of the measured observables.

The bound is computed using quantum fidelity between initial states.

Applications demonstrate the bound's relevance in quantum detection.

Abstract

Quantum fluctuations yield inevitable noises in quantum detection. We derive an upper bound of signal to noise ratio for arbitrary quantum detection described by trace-class operators with discrete spectra. The bound is independent of observables to be detected and is computed by quantum fidelity of two initial quantum states. We provide applications of the upper bound.