Improving QKD for Entangled States with Low Squeezing via Non-Gaussian Operations

TL;DR

This paper evaluates non-Gaussian operations like photon subtraction and quantum scissors to enhance continuous variable quantum key distribution over lossy channels, especially for low squeezing levels, with implications for satellite communication.

Contribution

It provides a comparative analysis of non-Gaussian operations applied at transmitter or receiver to improve CV-QKD performance under loss.

Findings

Receiver-side photon subtraction yields higher key rates above 1.5dB squeezing.

Transmitter-side quantum scissors are optimal below 1.5dB squeezing.

Non-Gaussian operations increase robustness of entangled states against loss.

Abstract

In this work we focus on evaluating the effectiveness of two non-Gaussian operations, photon subtraction (PS) and quantum scissors (QS) in terms of Continuous Variable (CV)-Quantum Key Distribution (QKD) over lossy channels. Each operation is analysed in two scenarios, one with the operation applied transmitter-side to a Two-Mode Squeezed Vacuum (TMSV) state and a second with the operation applied to the TMSV state receiver-side. We numerically evaluate the entanglement and calculate the QKD key rates produced in all four possible scenarios. Our results show that for a fixed value of initial squeezing in the TMSV state, the states produced by the non-Gaussian operations are more robust to loss, being capable of generating higher key rates for a given loss. More specifically, we find that for values of initial TMSV squeezing below 1.5dB the highest key rates are obtained by means of transmitter-QS. On the other hand, for squeezing above 1.5dB we find that receiver-PS produces higher key rates. Our results will be important for future CV-QKD implementations over free-space channels, such as the Earth-satellite channel. Accepted for Publication in Quantum Communications and Information Technology Workshop, IEEE Globecom, HI, USA, December 2019.