Cameron Trainor | Searcharxiv

arXiv2025

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

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.

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arXiv2023

Electromagnetically-induced transparency assists the Raman gradient echo memory at moderate detuning, dependent on gradient order

Optical quantum memories are essential for quantum communications and photonic quantum technologies. Ensemble optical memories based on 3-level interactions are a popular basis for implementing these memories. All such memories, however, suffer from loss due to scattering. In off-resonant 3-level interactions, such as the Raman gradient echo memory (GEM), scattering loss can be reduced by a large detuning from the intermediate state. In this work, we show how electromagnetically induced transparency adjacent to the Raman absorption line plays a crucial role in reducing scattering loss, so that maximum efficiency is in fact achieved at a moderate detuning. Furthermore, the effectiveness of the transparency, and therefore the efficiency of GEM, depends on the order in which gradients are applied to store and recall the light. We provide a theoretical analysis and show experimentally how the efficiency depends on gradient order and detuning.

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