Eur. Phys. J. D (2016) 70: 185
https://doi.org/10.1140/epjd/e2016-60662-3

Regular Article

Slow light enhanced atomic frequency comb quantum memories in photonic crystal waveguides^*

Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing 100084, P.R. China

^a e-mail: ycz13@mails.tsinghua.edu.cn

Received: 22 November 2015
Received in final form: 14 May 2016
Published online: 8 September 2016

Abstract

In this paper, we propose a slow light-enhanced quantum memory with high efficiency based on atomic frequency comb (AFC) in ion-doped photonic crystal waveguide (PCW). The performance of the quantum memory is investigated theoretically, considering the impact of the signal bandwidth. Both the forward and backward retrieval schemes are analyzed. In the forward retrieval scheme, the analysis shows that a moderate slow light effect can improve the retrieval efficiency to above 50% with very high fidelity, even when the intrinsic optical depth is very low and the signal bandwidth is comparable with the AFC bandwidth. In the backward retrieval scheme, retrieval efficiency larger than 90% can be obtained and fidelity can remain above 90% for signal with bandwidth much narrower than AFC bandwidth, when moderate slow light is introduced into waveguide with low intrinsic optical depth. Although the phase mismatching effect limits the slow light enhancement on retrieval efficiency and decreases the fidelity for signal with bandwidth approaching AFC bandwidth, we design a modified atomic frequency comb structure (MAFC) based on which a moderate slow light can make the retrieval efficiency larger than 85% and keep the fidelity above 80%. Our calculations show that the proposed scheme provides a promising way to realize high efficiency on-chip quantum memory.