Classicalization of Nonclassical Quantum States in Loss and Noise -- Some No-Go Theorems

TL;DR

This paper establishes rigorous no-go theorems showing that in high-loss, noisy quantum communication scenarios, nonclassical states do not offer significant advantages over classical states.

Contribution

It provides a formal framework and trace distance bounds demonstrating the limitations of nonclassical states in lossy, noisy environments, including applications like quantum illumination.

Findings

High loss and noise negate the advantage of nonclassical states

Rigorous bounds show no significant benefit of nonclassical states in practical scenarios

Quantum illumination does not outperform classical strategies under these conditions

Abstract

The general problem of performance advantage obtainable by the use of nonclassical transmitted states over classical ones is considered. Attention is focused on the situation where system loss is significant and additive Gaussian noise may be present at the receiver. Under the assumption that the total received state is classical, rigorous output density operator representations and their trace distance bounds are developed for classical and nonclassical transmitted states. For applications with high loss in all modes, a practical No-Go theorem is enunciated that rules out the possibility of significant advantage of nonclassical over classical states. The recent work on quantum illumination is discussed as an example of our no-go approach.