Continuous-variable measurement-device-independent quantum key distribution with virtual photon subtraction

TL;DR

This paper introduces a non-Gaussian post-selection method, equivalent to photon subtraction, to enhance the performance and security distance of continuous-variable measurement-device-independent quantum key distribution protocols.

Contribution

It proposes a novel non-Gaussian post-selection technique for CV-MDI QKD that improves key rate and noise tolerance, especially when applied solely by Alice.

Findings

Enhanced secret key rate at long distances.

Increased tolerable excess noise.

Optimal performance achieved with Alice's data selection.

Abstract

The method of improving the performance of continuous-variable quantum key distribution protocols by post-selection has been recently proposed and verified. In continuous-variable measurement-device-independent quantum key distribution (CV-MDI QKD) protocols, the measurement results are obtained from untrusted third party Charlie. There is still not an effective method of improving CV-MDI QKD by the post-selection with untrusted measurement. We propose a method to improve the performance of coherent-state CV-MDI QKD protocol by non-Gaussian post-selection. The non-Gaussian post-selection of transmitted data is equivalent to an ideal photon subtraction on the two-mode squeezed vacuum state, which is favorable to enhance the performance of CV-MDI QKD. In CV-MDI QKD protocol with non-Gaussian post-selection, two users select their own data independently. We demonstrate that the optimal performance of the renovated CV-MDI QKD protocol is obtained with the transmitted data only selected by Alice. By setting appropriate parameters of the non-Gaussian post-selection, the secret key rate and tolerable excess noise are both improved at long transmission distance. The method provides an effective optimization scheme for the application of CV-MDI QKD protocols.