Optimization of Broadband $\Lambda$-type Quantum Memory Using Gaussian Pulses

TL;DR

This paper explores optimizing broadband $ ext{Lambda}$-type quantum memory using Gaussian pulses, identifying a unique pulse duration that maximizes efficiency and approaches theoretical bounds, enhancing quantum memory performance.

Contribution

It introduces a method to optimize quantum memory efficiency with Gaussian pulses by identifying optimal pulse durations and control delays, simplifying experimental implementation.

Findings

Existence of a unique optimal pulse duration for maximum efficiency.

Optimized efficiency approaches the protocol-independent theoretical bound.

Saturation of efficiency over a broad range of pulse durations.

Abstract

Optical quantum memory--the ability to store photonic quantum states and retrieve them on demand--is an essential resource for emerging quantum technologies and photonic quantum information protocols. Simultaneously achieving high efficiency and high-speed, broadband operation is an important task necessary for enabling these applications. In this work, we investigate the optimization of a large class of optical quantum memory protocols based on resonant interaction with ensembles of $\Lambda$-type level systems with the restriction that the temporal envelope of all optical fields must be Gaussian, which reduces experimental complexity. We show that for overlapping signal and control fields there exists a unique and broadband pulse duration that optimizes the memory efficiency, and that this optimized efficiency can be close to the protocol-independent bound. We further optimize over the control field temporal delay and pulse duration, demonstrating saturation of this efficiency bound over a broad range of pulse durations while clarifying the underlying physics of the quantum memory interaction.