Multi-mode CV-QKD with Non-Gaussian Operations

TL;DR

This paper demonstrates that non-Gaussian operations in multi-mode CV-QKD systems can significantly enhance secret key rates over long distances, outperforming single-mode approaches and benefiting real-world quantum communication.

Contribution

It reveals that non-Gaussian operations can increase secret key rates in multi-mode CV-QKD, unlike in single-mode systems, especially at high losses.

Findings

Multi-mode non-Gaussian CV-QKD achieves higher key rates than single-mode.

At 30dB losses, multi-mode systems outperform single-mode by orders of magnitude.

Results are relevant for practical CV-QKD systems using quantum error correction.

Abstract

Non-Gaussian operations have been studied intensively in recent years due to their ability to increase the secret key rate for certain CV-QKD protocols. However, most previous studies on such protocols are carried out in a single-mode setting, even though in reality any quantum state contains multi-mode components in frequency space. In this work we investigate the use of non-Gaussian operations in a multi-mode CV-QKD system. Our main finding is that, contrary to single-mode CV-QKD systems, in generic multi-mode CV-QKD systems it is possible to use non-Gaussian operations to increase the optimized secret key rate. More specifically, we find that at losses of order 30dB, which represents a distance of order 160km and the effective maximum distance for CV-QKD, the key rate for multi-mode non-Gaussian operations can be orders of magnitude higher than single-mode operations. Our results are important for real-world CV-QKD systems especially those dependent on quantum error correction - a process that requires non-Gaussian effects.