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 104. 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.
@article{arxiv.1511.00349,
title = {Optical quantum memory for ultrafast photons using molecular alignment},
author = {G. S. Thekkadath and K. Heshami and D. G. England and P. J. Bustard and B. J. Sussman and M. Spanner},
journal= {arXiv preprint arXiv:1511.00349},
year = {2017}
}