Quantum repeater based on cavity-QED evolutions and coherent light

TL;DR

This paper introduces a cavity QED-based quantum repeater scheme that uses coherent light and atomic chains, avoiding complex quantum gates, and achieves effective entanglement distribution and purification for long-distance quantum communication.

Contribution

The paper presents a novel quantum repeater protocol utilizing cavity QED evolutions and coherent light, eliminating the need for two-qubit gates and ancillary entangled resources.

Findings

Achieves reasonable fidelities and repeater rates for long-distance communication.

Utilizes simple coherent state discrimination with beam splitter and detectors.

Avoids ancillary entangled resources in entanglement purification.

Abstract

In the framework of cavity QED, we propose a quantum repeater scheme that uses coherent light and chains of atoms coupled to optical cavities. In contrast to conventional repeater schemes, we avoid the usage of two-qubit quantum logical gates by exploiting solely the cavity QED evolution. In our previous paper [D. Gonta and P. van Loock: Phys. Rev. A 88, 052308 (2013)], we already proposed a quantum repeater in which the entanglement between two neighboring repeater nodes was distributed using controlled displacements of input coherent light, while the produced low-fidelity entangled pairs were purified using ancillary (four-partite) entangled states. In this paper, the entanglement distribution is realized using a sequence of controlled phase shifts and displacements of input coherent light. Compared to previous coherent-state-based distribution schemes for two-qubit entanglement, the present scheme relies only upon a simple discrimination of two coherent states with opposite signs, which can be performed in a quantum mechanically optimal fashion via a beam splitter and two on-off detectors. The entanglement purification utilizes a scheme that avoids the usage of ancillary entangled resources. Our repeater scheme exhibits reasonable fidelities and repeater rates providing an attractive platform for long-distance quantum communication.