Repeaters for Continuous Variable Quantum Communication

TL;DR

This paper proposes a continuous variable quantum repeater design capable of distributing entangled states over thousands of kilometers with polynomial success probability, advancing long-distance quantum communication.

Contribution

It introduces a novel quantum repeater scheme combining non-Gaussian operations, Gaussification, and heralded entanglement swapping to improve long-distance quantum communication.

Findings

Secure key can be generated over thousands of kilometers.

Success probability scales polynomially with distance.

Scheme enables long-distance quantum key distribution.

Abstract

Optical telecommunication is at the heart of today's internet and is currently enabled by the transmission of intense optical signals between remote locations. As we look to the future of telecommunication, quantum mechanics promise new ways to be able to transmit and process that information. Demonstrations of quantum key distribution and quantum teleportation using multi-photon states have been performed, but only over ranges limited to one hundred kilometers. To go beyond this, we need repeaters that are compatible with these quantum multi-photon continuous variables pulses. Here we present a design for a continuous variable quantum repeaters that can distribute entangled and pure two-mode squeezed states over arbitrarily long distances with a success probability that scales only polynomially with distance. The proposed quantum repeater is composed from several basic known building blocks such as non-Gaussian operations for entanglement distillation and an iterative Gaussification protocol (for retaining the Gaussian character of the final state), but complemented with a heralded non-Gaussian entanglement swapping protocol, which allows us to avoid extensive iterations of quantum Gaussification. We characterize the performance of this scheme in terms of key rates for quantum key distribution and show a secure key can be generated over thousands of kilometers.