Measurement-Based Noiseless Linear Amplification for Quantum Communication

TL;DR

This paper demonstrates a measurement-based noiseless linear amplification technique that enhances entanglement and enables secret key extraction over long-distance quantum communication channels, offering practical advantages over physical amplifiers.

Contribution

It introduces a measurement-based noiseless linear amplifier for quantum communication, improving entanglement and security over lossy channels with easier implementation.

Findings

Effective entanglement stronger than passively transmitted resources

Successful secret key extraction in insecure regimes

Advantages over physical amplifiers in implementation and success probability

Abstract

Entanglement distillation is an indispensable ingredient in extended quantum communication networks. Distillation protocols are necessarily non-deterministic and require advanced experimental techniques such as noiseless amplification. Recently it was shown that the benefits of noiseless amplification could be extracted by performing a post-selective filtering of the measurement record to improve the performance of quantum key distribution. We apply this protocol to entanglement degraded by transmission loss of up to the equivalent of 100km of optical fibre. We measure an effective entangled resource stronger than that achievable by even a maximally entangled resource passively transmitted through the same channel. We also provide a proof-of-principle demonstration of secret key extraction from an otherwise insecure regime. The measurement-based noiseless linear amplifier offers two advantages over its physical counterpart: ease of implementation and near optimal probability of success. It should provide an effective and versatile tool for a broad class of entanglement-based quantum communication protocols.