Capacity-approaching quantum repeaters for quantum communications

TL;DR

This paper presents a novel continuous-variable quantum repeater design that can achieve near-capacity quantum communication rates over long distances, even in noisy conditions, surpassing existing bounds.

Contribution

The authors propose a practical quantum repeater setup using noiseless linear amplifiers, quantum memories, and Bell measurements, demonstrating its ability to approach theoretical capacities.

Findings

Achieves quantum communication rates surpassing the PLOB bound in noisy regimes.

Develops a non-ideal model for continuous-variable quantum memories.

Shows potential rate deviations due to noise and device imperfections.

Abstract

In present-day quantum communications, one of the main problems is the lack of a quantum repeater design that can simultaneously secure high rates and long distances. Recent literature has established the end-to-end capacities that are achievable by the most general protocols for quantum and private communication within a quantum network, encompassing the case of a quantum repeater chain. However, whether or not a physical design exists to approach such capacities remains a challenging objective. Driven by this motivation, in this work, we put forward a design for continuous-variable quantum repeaters and show that it can actually achieve the feat. We also show that even in a noisy regime our rates surpass the Pirandola-Laurenza-Ottaviani-Banchi (PLOB) bound. Our repeater setup is developed upon using noiseless linear amplifiers, quantum memories, and continuous-variable Bell measurements. We, furthermore, propose a non-ideal model for continuous-variable quantum memories that we make use of in our design. We then show that potential quantum communications rates would deviate from the theoretical capacities, as one would expect, if the quantum link is too noisy and/or low-quality quantum memories and amplifiers are employed.