Quantum repeaters based on heralded qubit amplifiers

TL;DR

This paper proposes a quantum repeater scheme utilizing heralded qubit amplifiers, enabling high-fidelity entanglement distribution over long distances without the need for postselection, suitable for device-independent quantum key distribution.

Contribution

It introduces a quantum repeater architecture based on a heralded qubit amplifier that purifies imperfections, allowing high-rate, long-distance entanglement distribution without postselection.

Findings

High-fidelity entanglement over long distances achieved

Purification of imperfections via entanglement swapping

Potential for device-independent quantum key distribution

Abstract

We present a quantum repeater scheme based on the recently proposed qubit amplifier [N. Gisin, S. Pironio and N. Sangouard, Phys. Rev. Lett. 105, 070501 (2010)]. It relies on a on-demand entangled-photon pair source which uses on-demand single-photon sources, linear optical elements and atomic ensembles. Interestingly, the imperfections affecting the states created from this source, caused e.g. by detectors with non-unit efficiencies, are systematically purified from an entanglement swapping operation based on a two-photon detection. This allows the distribution of entanglement over very long distances with a high fidelity, i.e. without vacuum components and multiphoton errors. Therefore, the resulting quantum repeater architecture does not necessitate final postselections and thus achieves high entanglement distribution rates. This also provides unique opportunities for device-independent quantum key distribution over long distances with linear optics and atomic ensembles.