Demonstration of a photonic time-frequency Fourier transform and temporal double slit using atomic quantum memory

TL;DR

This paper demonstrates a quantum memory-based Fourier transform for light using rubidium atoms, enabling manipulation of quantum states in the time-frequency domain for advanced quantum communication.

Contribution

It introduces a novel in-memory Fourier transform combining Gradient Echo Memory and Electromagnetically Induced Transparency protocols in a quantum memory system.

Findings

Successful implementation of in-memory Fourier transform

Observation of interference dependent on phase and timing

Potential for quantum optical system applications

Abstract

A quantum memory for light is expected to play a crucial role in quantum communication protocols and distributed quantum computing. In addition to storage and buffering, a quantum memory can be used for manipulations of stored states to allow more complex quantum network operations. In this work, we demonstrate an in-memory Fourier transform using a combination of two well-established quantum memory protocols: Gradient Echo Memory and Electromagnetically Induced Transparency. Our experiment is realised using an ensemble of rubidium atoms that are laser cooled in an elongated magneto-optic trap to maximise optical depth. The results of our time-frequency Fourier transform can be understood as a temporal double slit. We show that the interference between time-separated pulses depends on the relative phase and time between the pulses of light. The use of a quantum memory enables us to illuminate exactly where and how interference occurs between time separated pulses. Time-frequency Fourier manipulation is a well established technique in classical optical systems. Our combination of Fourier manipulation and quantum-compatible memory could be used to bring similar capability to quantum optical systems.