Overcoming lossy channel bounds using a single quantum repeater node

TL;DR

This paper introduces a simple quantum repeater scheme that enables quantum key distribution with higher efficiency than direct transmission, potentially surpassing fundamental channel loss limits using current technology.

Contribution

A novel, practical quantum repeater protocol that improves key rates by leveraging quantum memories and outperforms direct transmission schemes within realistic parameters.

Findings

Secret key rate scales as the square root of transmittivity.

Protocol outperforms direct transmission under certain realistic imperfections.

Implementation feasible with current quantum technology.

Abstract

We propose a scheme for performing quantum key distribution (QKD) which has the potential to beat schemes based on the direct transmission of photons between the communicating parties. In our proposal, the communicating parties exchange photons with two quantum memories placed between them. This is a very simple quantum repeater scheme and can be implemented with currently available technology. Ideally, its secret key rate scales as the square root of the transmittivity of the optical channel, which is superior to QKD schemes based on direct transmission because key rates for the latter scale at best linearly with transmittivity. Taking into account various imperfections in each component of our setup, we present parameter regimes in which our protocol outperforms protocols based on direct transmission.