Determining phase coherence time of stored light in warm atomic vapor

Taek Jeong,Han Seb Moon,Jumi Park

doi:10.1038/s41598-017-15469-4

Abstract

In quantum memory based on an atomic medium, we may have a question about whether all information on the stored light is preserved. In particular, the phase coherence between the stored and retrieval light pulses is very interesting, because it can indicate the relationship between the coherence time and storage time of the light. In this paper, we investigate the phase coherence time of light stored in a warm atomic vapor, by examining the beat-note interference between the retrieval light pulse and a reference light beam optically delayed using an optical fiber. The beat-note interference fringes are measured for different reference-light optical delays. The observed retrieval-light phase indicates that the phase of the input probe light is preserved in the medium. However, we further confirm that the retrieval-light phase coherence depends on the phase coherence of the coupling light used for retrieval in the storage process.

Highlights

The phenomenon of light storage in an atomic medium is widely regarded as important, having application in various fields, such as atomic physics, quantum optics, quantum computing, and quantum communication[1,2,3,4,5,6,7,8,9,10]
By comparing the longitudinal phase coherence of the probe light and coupling light with that between the storage and retrieval light pulses using a delayed beat-note interferometer, we directly demonstrate that the longitudinal phase coherence of the retrieval light pulse is dependent on the phase coherence of the coupling light beams used for writing and reading in electromagnetically induced transparency (EIT)-based atomic light storage
The reference light, which was shifted by 2 MHz from the optical frequency of the probe laser, was sent to an optical delay line consisting of three 400-m-long single-mode fibers (SMFs)

Summary

Introduction

The phenomenon of light storage in an atomic medium is widely regarded as important, having application in various fields, such as atomic physics, quantum optics, quantum computing, and quantum communication[1,2,3,4,5,6,7,8,9,10]. Techniques for the storage and manipulation of the quantum state of an optical light pulse have been successfully developed to facilitate quantum memory in an atomic medium with atomic coherence. Previous studies have described preservation of the longitudinal phase coherence of a retrieval light pulse in an atomic vapor cell[14] and a cold atomic medium[15]. Preservation of the properties of the retrieval light pulse in light storage and quantum memory has been studied[14,15], the phase coherence of the retrieval light pulse has never been directly compared to that of the input light. We investigate the longitudinal phase coherence of a retrieval light pulse according to the storage and delay times of a reference light in a warm Rb atomic vapor. By comparing the longitudinal phase coherence of the probe light and coupling light with that between the storage and retrieval light pulses using a delayed beat-note interferometer, we directly demonstrate that the longitudinal phase coherence of the retrieval light pulse is dependent on the phase coherence of the coupling light beams used for writing and reading in EIT-based atomic light storage

Methods

Results

Conclusion