Tight bound on coherent-state-based entanglement generation over lossy channels

TL;DR

This paper establishes a tight upper bound on the performance of coherent-state-based entanglement generation over lossy channels, showing it is solely determined by channel loss and achievable with a simple linear optical protocol.

Contribution

The paper derives the first tight upper bound on entanglement generation performance based on channel loss and demonstrates its achievability with a practical linear optical protocol.

Findings

The performance limit depends only on channel loss.

A simple linear optical protocol can reach this performance bound.

The bound guides optimal entanglement generation in quantum repeaters.

Abstract

The first stage of the hybrid quantum repeaters is entanglement generation based on transmission of pulses in coherent states over a lossy channel. Protocols to make entanglement with only one type of error are favorable for rendering subsequent entanglement distillation efficient. Here we provide the tight upper bound on performances of these protocols that is determined only by the channel loss. In addition, we show that this bound is achievable by utilizing a proposed protocol [arXiv:0811.3100] composed of a simple combination of linear optical elements and photon-number-resolving detectors.