A Quantum Repeater Node Demonstrating Unconditionally Secure Key Distribution

TL;DR

This paper demonstrates a quantum repeater node with two atoms that enables unconditionally secure key distribution over longer distances, showing improved key rate and error thresholds for quantum networks.

Contribution

The work introduces a functional quantum repeater node with two memory atoms, advancing secure quantum communication by overcoming photon loss and scaling limitations.

Findings

Increased effective attenuation length by a factor of two

Achieved unconditionally secure key distribution surpassing 11% error rate threshold

Demonstrated scaling advantage of the key rate

Abstract

Long-distance quantum communication requires quantum repeaters to overcome photon loss in optical fibers. Here we demonstrate a repeater node with two memory atoms in an optical cavity. Both atoms are individually and repeatedly entangled with photons that are distributed until each communication partner has independently received one of them. An atomic Bell-state measurement followed by classical communication serves to establish a key. We demonstrate scaling advantage of the key rate, increase the effective attenuation length by a factor of two, and beat the error-rate threshold of 11\% for unconditionally secure communication, the corner stones for repeater-based quantum networks.