Entanglement-based linear-optical qubit amplifier

TL;DR

This paper introduces a linear-optical qubit amplifier utilizing entangled ancillae that maintains high success probability at increased gain and can restore entanglement lost over lossy channels, enhancing quantum communication.

Contribution

It presents a novel entanglement-based linear-optical qubit amplifier with non-vanishing success probability at high gain, improving upon previous designs.

Findings

Success probability remains high at increased gain

Device can restore entanglement after transmission loss

Enables higher secure key rates in quantum key distribution

Abstract

We propose a linear-optical scheme for an efficient amplification of a photonic qubit based on interaction of the signal mode with a pair of entangled ancillae. In contrast to a previous proposal for qubit amplifier by Gisin et al., [Phys Rev. Lett. 105, 070501 (2010)] the success probability of our device does not decrease asymptotically to zero with increasing gain. Moreover we show how the device can be used to restore entanglement deteriorated by transmission over a lossy channel and calculate the secure key rate for device-independent quantum key distribution.