# Universal upper bounds for Gaussian information capacity

## TL;DR

This paper derives new universal upper bounds on the information capacity of bosonic Gaussian channels with general Gaussian noise using the quantum entropy power inequality, extending previous results beyond thermal noise models.

## Contribution

It introduces a generalized Gaussian noise model and provides a rigorous method to calculate upper bounds on channel capacity using QEPI.

## Key findings

- Established new upper bounds for Gaussian-noise channels
- Extended capacity bounds beyond thermal noise assumptions
- Utilized QEPI for a novel capacity estimation approach

## Abstract

The most natural way to describe an information-carrying system containing a specific noise is an additive white Gaussian-noise (AWGN) channel. In bosonic quantum systems (especially the Gaussian case), although the classical information capacity for a phase-insensitive and thermal-noise channel is additive based on a proof of the minimum output entropy conjecture, several open questions remain. By generalizing the Gaussian noise model from thermal noise to general Gaussian noise, we rigorously revisit and calculate these strong upper bounds on the information capacity for single-mode with general Gaussian-noise channels. In this study, we use the quantum entropy power inequality (QEPI) approach. This framework gives a new formula for finding upper bounds on the information capacity of bosonic Gaussian channels.