Radio-frequency driven dipole-dipole interactions in spatially separated volumes

TL;DR

This paper demonstrates how radio-frequency fields can induce and control resonant energy transfer between spatially separated cold Rydberg atoms, revealing multi-photon processes and enabling high-resolution spectroscopy.

Contribution

It introduces a method to use rf-fields to resonantly couple Rydberg atoms in separate volumes, with detailed analysis of interaction strength and resonance features.

Findings

Resonant energy transfer at 33 GHz between Rydberg atoms was achieved.

Multi-photon transitions up to fifth order were observed.

Resonance widths were reduced enabling sub-MHz spectroscopy.

Abstract

Radio-frequency (rf) fields in the MHz range are used to induce resonant energy transfer between cold Rydberg atoms in spatially separated volumes. After laser preparation of the Rydberg atoms, dipole-dipole coupling excites the 49s atoms in one cylinder to the 49p state while the 41d atoms in the second cylinder are transferred down to the 42p state. The energy exchanged between the atoms in this process is 33 GHz. An external rf-field brings this energy transfer into resonance. The strength of the interaction has been investigated as a function of amplitude (0-1 V/cm) and frequency (1-30 MHz) of the rf-field and as a function of a static field offset. Multi-photon transitions up to fifth order as well as selection rules prohibiting the process at certain fields have been observed. The width of the resonances has been reduced compared to earlier results by switching off external magnetic fields of the magneto-optical trap, making sub-MHz spectroscopy possible. All features are well reproduced by theoretical calculations taking the strong ac-Stark shift due to the rf-field into account.