Strong zero-field F\"orster resonances in K-Rb Rydberg systems

TL;DR

This paper investigates F"orster resonances in K-Rb Rydberg systems, revealing an ultrastrong, zero-field resonance with extensive interaction range, enabling advanced quantum information applications like entanglement and optical transistors.

Contribution

It identifies a novel ultrastrong zero-field F"orster resonance in K-Rb Rydberg atoms with large crossover distance, enhancing long-range quantum interactions.

Findings

Discovery of an ultrastrong, zero-field F"orster resonance in K-Rb systems.

Resonance exhibits isotropic behavior over various external field orientations.

Potential for implementing high-rate Rydberg-based quantum devices.

Abstract

We study resonant dipole-dipole coupling and the associated van der Waals energy shifts in Rydberg excited atomic rubidium and potassium and investigate F\"orster resonances between interspecies pair states. A comprehensive survey over experimentally accessible pair state combinations reveals multiple candidates with small F\"orster defects. We crucially identify the existence of an ultrastrong, "low" electric field K-Rb F\"orster resonance with a extremely large zero-field crossover distance exceeding 100 $\mu$m between the van der Waals regime and the resonant regime. This resonance allows for a strong interaction over a wide range of distances and by investigating its dependence on the strength and orientation of external fields we show this to be largely isotropic. As a result, the resonance offers a highly favorable setting for studying long-range resonant excitation transfer and entanglement generation between atomic ensembles in a flexible geometry. The two-species K-Rb system establishes a unique way of realizing a Rydberg single-photon optical transistor with a high-input photon rate and we specifically investigate an experimental scheme with two separate ensembles.