Quantum capacity of lossy channel with additive classical Gaussian noise : a perturbation approach

TL;DR

This paper investigates the quantum capacity of lossy channels with additive classical Gaussian noise, demonstrating that non-Gaussian perturbations reduce transmission efficiency at high input energies using a first-order perturbation approach.

Contribution

It introduces a perturbation method to analyze the quantum capacity of noisy channels, revealing the suboptimality of non-Gaussian inputs in high-energy regimes.

Findings

Non-Gaussian perturbations decrease quantum capacity at high energies.

First-order perturbation analysis shows Gaussian states are optimal inputs.

The approach applies to channels with multiple input copies.

Abstract

For a quantum channel of additive Gaussian noise with loss, in the general case of $n$ copies input, we show that up to first order perturbation, any non-Gaussian perturbation to the product thermal state input has a less quantum information transmission rate when the input energy tend to infinitive.