Dipolar exchange induced transparency with Rydberg atoms

TL;DR

This paper demonstrates that dipole-dipole exchange interactions with Rydberg atoms can induce transparency in an atomic medium, enabling control over photon transmission based on the number of spins and photons involved.

Contribution

It introduces a novel mechanism where Rydberg atom interactions serve as a control for photon transparency, differing from traditional EIT by using exchange interactions instead of control fields.

Findings

Single spin Rydberg state induces transparency for one photon.

Multiple spins allow transparency for up to the number of spins.

Photon group velocity depends on the number of photons and spins.

Abstract

A three-level atomic medium can be made transparent to a resonant probe field in the presence of a strong control field acting on an adjacent atomic transition to a long-lived state, which can be represented by a highly excited Rydberg state. The long-range interactions between the Rydberg state atoms then translate into strong, non-local, dispersive or absorptive interactions between the probe photons, which can be used to achieve deterministic quantum logic gates and single photon sources. Here we show that long-range dipole-dipole exchange interaction with one or more spins -- two-level systems represented by atoms in suitable Rydberg states -- can play the role of control field for the optically-dense medium of atoms. This induces transparency of the medium for a number of probe photons $n_p$ not exceeding the number of spins $n_s$, while all the excess photons are resonantly absorbed upon propagation. In the most practical case of a single spin atom prepared in the Rydberg state, the medium is thus transparent only to a single input probe photon. For larger number of spins $n_s$, all $n_p \leq n_s$ photon components of the probe field would experience transparency but with an $n_p$-dependent group velocity.