Engineering long-range interactions between ultracold atoms with light

TL;DR

This paper proposes a laser-based method to control ultracold atomic collisions by inducing long-range repulsive interactions, effectively preventing inelastic losses in dilute quantum gases.

Contribution

It introduces an optical shielding technique using laser coupling to engineer repulsive interactions at large distances between ultracold atoms, reducing inelastic collisions.

Findings

Almost complete suppression of inelastic collisions predicted.

Laser parameters (Rabi frequency and detuning) effectively control the shielding.

Method applicable to various bi-alkali-metal pairs.

Abstract

Ultracold temperatures in dilute quantum gases opened the way to an exquisite control of matter at the quantum level. Here we focus on the control of ultracold atomic collisions using a laser to engineer their interactions at large interatomic distances. We show that the entrance channel of two colliding ultracold atoms can be coupled to a repulsive collisional channel by the laser light so that the overall interaction between the two atoms becomes repulsive: this prevents them to come close together and to undergo inelastic processes, thus protecting the atomic gases from unwanted losses. We illustrate such an optical shielding mechanism with potassium and cesium atoms colliding at ultracold temperature (\textless 1 microkelvin). The process is described in the framework of the dressed-state picture and we then solve the resulting staionary coupled Schr\"{o}dinger equations. The role of spontaneous emission and photoinduced inelastic scattering is also investigated as possible limitations of the shielding efficiency. We predict an almost complete suppression of inelastic collisions using a laser-induced coupling characterized by a Rabi frequency of $\omega = 200$~MHz and a frequency detuned from the potassium D2 transition by $\Delta = 200$~MHz. We found the polarization of the laser has no influence on this efficiency. This proposal could easily be formulated for other bi-alkali-metal pairs as their long-range interaction are all very similar to each other.