Heralded high-efficiency quantum repeater with atomic ensembles assisted by faithful single-photon transmission.

Tao Li,Fu-Guo Deng

doi:10.1038/srep15610

Abstract

Quantum repeater is one of the important building blocks for long distance quantum communication network. The previous quantum repeaters based on atomic ensembles and linear optical elements can only be performed with a maximal success probability of 1/2 during the entanglement creation and entanglement swapping procedures. Meanwhile, the polarization noise during the entanglement distribution process is harmful to the entangled channel created. Here we introduce a general interface between a polarized photon and an atomic ensemble trapped in a single-sided optical cavity, and with which we propose a high-efficiency quantum repeater protocol in which the robust entanglement distribution is accomplished by the stable spatial-temporal entanglement and it can in principle create the deterministic entanglement between neighboring atomic ensembles in a heralded way as a result of cavity quantum electrodynamics. Meanwhile, the simplified parity-check gate makes the entanglement swapping be completed with unity efficiency, other than 1/2 with linear optics. We detail the performance of our protocol with current experimental parameters and show its robustness to the imperfections, i.e., detuning and coupling variation, involved in the reflection process. These good features make it a useful building block in long distance quantum communication.

Highlights

Due to the low probability of Stokes photon emission required in the Duan-Lukin-Cirac-Zoller (DLCZ) proposal[17], the parties can hardly establish the entanglement efficiently for quantum entanglement swapping
Since the two-photon interference is performed with the polarization degree of freedom (DOF) of the photons[21,22], which is incident to be influenced by the thermal fluctuation, vibration, and the imperfection of the fiber[29], the fidelity of the entanglement created between the neighboring nodes will be decreased when the photons are transmitted directly[6,7]
We show that a deterministic faithful entanglement distribution in a quantum repeater can be implemented with the time-bin photonic state when two identical fibers act as the channels of different spatial DOFs of the photons

Summary

Introduction

Due to the low probability of Stokes photon emission required in the Duan-Lukin-Cirac-Zoller (DLCZ) proposal[17], the parties can hardly establish the entanglement efficiently for quantum entanglement swapping. We show that a deterministic faithful entanglement distribution in a quantum repeater can be implemented with the time-bin photonic state when two identical fibers act as the channels of different spatial DOFs of the photons It does not require fast PCs and the time-slot discriminator[29,30,31,32,33] is not needed anymore. By using the input-output process of a single photon based on our general interface, the entanglement between the neighboring atom ensembles can be created in a heralded way, without any classical communication after the clicks of the photon detectors, and the quantum swapping can be implemented with almost unitary success probability by a simplified parity-check gate (PCG) between two ensembles, other than 1/2 with linear optics. These good features will make it a useful building block in long-distance quantum communication in future

Methods

Results

Conclusion