Quantum reading under a local energy constraint

TL;DR

This paper investigates quantum reading performance under a local energy constraint, demonstrating conditions where nonclassical light sources outperform classical ones in retrieving information from digital memories.

Contribution

It introduces an analysis of quantum reading with a local energy constraint, identifying the critical number of modes needed for nonclassical sources to surpass classical performance.

Findings

Nonclassical sources outperform classical ones after a certain number of modes.

The analysis under local energy constraints differs from previous global energy constraint studies.

The critical number of modes for quantum advantage is characterized.

Abstract

Nonclassical states of light play a central role in many quantum information protocols. Their quantum features have been exploited to improve the readout of information from digital memories, modelled as arrays of microscopic beam splitters [S. Pirandola, Phys. Rev. Lett. 106, 090504 (2011)]. In this model of quantum reading, a nonclassical source of light with Einstein-Podolski-Rosen correlations has been proven to retrieve more information than any classical source. In particular, the quantum-classical comparison has been performed under a global energy constraint, i.e., by fixing the mean total number of photons irradiated over each memory cell. In this paper we provide an alternative analysis which is based on a local energy constraint, meaning that we fix the mean number of photons per signal mode irradiated over the memory cell. Under this assumption, we investigate the critical number of signal modes after which a nonclassical source of light is able to beat any classical source irradiating the same number of signals.