Optical quantum memory for ultrafast photons using molecular alignment

TL;DR

This paper proposes a novel quantum memory scheme using molecular alignment to store ultrafast photons in atomic ensembles, enabling high time-bandwidth products and potential room-temperature implementation.

Contribution

It introduces a method to store ultrafast photons via a time-dependent refractive index from molecular alignment, extending storage times and bandwidths.

Findings

Successfully demonstrated storage of 50 fs pulses

Achieved storage times up to 20 ps, extendable to 1 ns

Time-bandwidth product of order 10^4

Abstract

The absorption of broadband photons in atomic ensembles requires either an effective broadening of the atomic transition linewidth, or an off-resonance Raman interaction. Here we propose a scheme for a quantum memory capable of storing and retrieving ultrafast photons in an ensemble of two-level atoms by using a propagation medium with a time-dependent refractive index generated from aligning an ensemble of gas-phase diatomic molecules. The refractive index dynamics generates an effective longitudinal inhomogeneous broadening of the two-level transition. We numerically demonstrate this scheme for storage and retrieval of a weak pulse as short as 50 fs, with a storage time of up to 20 ps. With additional optical control of the molecular alignment dynamics, the storage time can be extended about one nanosecond leading to time-bandwidth products of order $10^4$. This scheme could in principle be achieved using either a hollow-core fiber or a high-pressure gas cell, in a gaseous host medium comprised of diatomic molecules and a two-level atomic vapor at room temperature.