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.
Highlights
In recent years, ultracold Rydberg atoms have emerged as a prominent resource for numerous quantum-enabled technologies including quantum information processing [1], quantum simulation [2,3], quantum nonlinear optics [4], and hybrid quantum devices [5]
We have investigated the dipole-dipole interaction between rubidium and potassium atoms in their Rydberg states for a wide range of principal quantum numbers, and in particular we considered pair states comprising angular momentum channels that are amenable to two-photon Rydberg excitations
Using large spin-independent interaction coefficients C3k and small Förster defects as the figures of merit, we identified several strong Förster resonances with extremely small Förster defects at zero field
Summary
Ultracold Rydberg atoms have emerged as a prominent resource for numerous quantum-enabled technologies including quantum information processing [1], quantum simulation [2,3], quantum nonlinear optics [4], and hybrid quantum devices [5]. Förster resonances are a highly useful tool in ultracold Rydberg physics, as they enable fast external control of the strength and angular variation of Rydberg interactions [28], extend the range of Rydberg blockade by allowing a relatively slow 1/R3 fall-off, and can realize long-distance dipolar exchange of states between atoms or atomic ensembles [29]. We study Förster resonances arising in the dipole-dipole interaction between rubidium and potassium atoms in their Rydberg states. We observe a number of near Förster resonances with fortuitously small zero-field Förster defects resulting in a 1/R3 scaling in energy shift for distances up to 100 μm. These near resonances can further be brought to exact resonance by applying very small electric fields (
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