Spectroscopic Observation of Resonant Electric Dipole-Dipole Interactions between Cold Rydberg Atoms

Abstract

Resonant electric dipole-dipole interactions between cold Rydberg atoms were observed using microwave spectroscopy. Laser-cooled 85 Rb atoms in a magneto-optical trap were optically excited to 45d 5/2 Rydberg states using a pulsed laser. A microwave pulse transferred a fraction of these Rydberg atoms to the 46p 3/2 state. A second microwave pulse then drove atoms in the 45d 5/2 state to the 46d 5/2 state, and was used as a probe of interatomic interactions. The spectral width of this two-photon probe transition was found to depend on the presence of the 46p 3/2 atoms, and is due to the resonant electric dipole-dipole interaction between 45d 5/2 and 46p 3/2 Rydberg atoms.PACS numbers: 32.80. Rm, 34.20.Cf, 32.80.Pj The vast separation of the electron and ion-core in high-n Rydberg atoms is responsible for their large transition dipole moments [1]. These dipole moments dictate the strength of the dipole-dipole interaction between pairs of atoms. Therefore, excitation to Rydberg states allows one to turn on strong interactions between atoms which would otherwise be negligible. This has recently received considerable attention in the context of quantum information processing with cold neutral atoms [2,3,4,5,6,7]. For example, it has been proposed that a single excited Rydberg atom in a cloud may block further resonant excitation due to the dipole-dipole interaction -a process known as "dipole blockade" [3]. This would allow clouds of cold atoms to store qubits without the addressing of individual atoms and may also be useful for constructing single-atom and single-photon sources [5].Non-resonant dipole-dipole (van der Waals) interactions between Rydberg atoms were first observed by Raimond et al.[8] using spectral line broadening. Recently it has been shown that Rydberg excitation densities in a magneto-optical trap (MOT) are limited by these interactions [9,10]. Dipole-dipole interactions between Rydberg atoms have also been studied in the context of resonant energy transfer [1]. Of particular relevance to this work is the observation of resonant energy transfer between cold Rydberg atoms [11,12], where the Rydberg atoms behave more like an amorphous solid than a gas, and one cannot solely consider binary interactions to explain the transfer process [13,14]. However, use of the resonant dipole-dipole interaction between cold Rydberg atoms to influence radiative transitions -as presented in this work -is an unexplored area.We excite Rydberg states using a pulsed laser with no stringent demands on linewidth or stability. Dipoledipole interactions are then introduced and probed using microwave transitions between Rydberg states. This is advantageous since commercial microwave synthesizers are readily tunable, highly stable, and have easily adjustable powers and pulse-widths, as compared to lasers. Using this approach we have made the first spectroscopic observation of the resonant dipole-dipole interaction between cold Rydberg atoms using radiative transitions.To observe interactions between atoms that are effectiv...

Spectral linewidth broadening from pair fluctuations in a frozen Rydberg gas

“…There have been many experiments exploring the quantum manybody effects in Rydberg gases, e.g. spectral line broadening [1,2,3], number correlation [6,12,13] and collective excitation [8]. Many experimental results can be understood from the well-known dipole blockade effect: when two Rydberg atoms are close enough, the dipolar interaction will shift them out of resonance with the external driving laser, thus double excitation is greatly suppressed.…”

“…Ee,34.20.Cf Rydberg gases have attracted renewed interest in recent years due to the unprecedented advancement in laser cooling and trapping [1,2,3,4,5,6,7,8,9]. Rydberg atoms, possessing a large dipole moment and long lifetime, can interact with each other coherently for relatively long times, which make it a potential candidate for quantum information processing [10,11].…”

External Control of Electron Temperature in Ultra-Cold Plasmas

“…al. [18]. We probe the dipole-dipole interactions using mm-wave transitions between Rydberg states, and in so doing, make an adequate diagnosis of our Rydberg densities: if we can achieve the spectral broadening proposed by Raimon et.…”

“…al. [18] then we have achieved the density regime necessary to explore Rydberg to plasma formation and successive plasma dynamics.…”

Short-Range Interaction Impact on Two-Dimensional Dipolar Scattering

“…One can mention a gas of dipolar atoms or ultracold polar molecules in quasi-2D geometry of magneto-optical traps [1] and dipolar Rydberg atoms [2]. Beside the gas of polar molecules long range dipolar interaction also arises in a gas of 2D dipolar excitons in 2D quantum well of semiconductor heterostructures.…”