Quantum reading capacity under thermal and correlated noise

TL;DR

This paper investigates the quantum reading capacity of optical memories, demonstrating that quantum strategies outperform classical ones, especially under thermal and correlated noise, and are more robust at low power levels.

Contribution

It introduces a model for quantum reading of optical memories considering thermal and correlated noise, showing quantum advantage over classical methods in these noisy regimes.

Findings

Quantum reading capacity exceeds classical capacity in relevant settings.

Quantum reading is more robust than classical under thermal noise at low power.

Correlated noise affects reading rates but quantum methods maintain advantage.

Abstract

Quantum communication theory sets the maximum rates at which information can be encoded and decoded reliably given the physical properties of the information carriers. Here we consider the problem of readout of a digital optical memory, where information is stored by means of the optical properties of the memory cells that are in turn probed by shining a laser beam on them. Interesting features arise in the regime in which the probing light has to be treated quantum mechanically. The maximum rate of reliable readout defines the quantum reading capacity, which is proven to overcome the classical reading capacity, obtained by probing with classical light, in several relevant settings. We consider a model of optical memory in which information is encoded in the (complex-valued) attenuation factor and study the effects on the reading rates of thermal and correlated noise. The latter type of noise arises when the effects of wave diffraction on the probing light beam are taken into account. We discuss the advantages of quantum reading over the classical one and show that the former is substantially more robust than the latter under thermal noise in the regime of low power per pulse.