Long-distance high-fidelity continuous-variable quantum key distribution with non-Gaussian operations: An exact closed form solution

TL;DR

This paper derives an exact closed-form solution for a CV-QKD protocol with non-Gaussian operations, demonstrating enhanced range and fidelity through optimized parameters, approaching fundamental communication limits.

Contribution

It provides a novel closed-form expression for the output state in CV-QKD with non-Gaussian operations and optimizes parameters to improve protocol performance.

Findings

Range is within 6.5% of fundamental limit in pure loss channels

Trade-off between protocol range and fidelity with excess noise

Optimized parameters significantly enhance protocol performance

Abstract

In this paper, we derive a closed form expression for the output state of a CV-QKD protocol in the presence of zero-photon catalysis (ZPC) and quantum scissor (QS). Then, based on this closed form solution, we use direct search algorithm to find the appropriate values of input state and QS parameters, which considerably enhance the range and the fidelity of a CV-QKD protocol. In the special case of pure loss channel, the largest range of the protocol is only 6.5% less than the fundamental limit of repeaterless quantum communication. In addition, examination of the protocol for different values of excess noise, reveals that their is a trade-off between range and fidelity, and high value of fidelity can be obtained at the cost of a slight reduction in protocol range.