Abstract
We report on time-resolved pulsed four-wave mixing (FWM) signals in a thermal Rubidium vapor involving a Rydberg state. We observe FWM signals with dephasing times up to 7 ns, strongly dependent on the excitation bandwidth to the Rydberg state. The excitation to the Rydberg state is driven by a pulsed two-photon transition on ns timescales. Combined with a cw de-excitation laser, a strongly directional and collective emission is generated according to a combination of the phase matching effect and averaging over Doppler classes. In contrast to a previous report (Huber et al. in Phys Rev A 90: 053806, 2014) using off-resonant FWM, at a resonant FWM scheme we observe additional revivals of the signal shortly after the incident pulse has ended. We infer that this is a revival of motion-induced constructive interference between the coherent emissions of the thermal atoms. The resonant FWM scheme reveals a richer temporal structure of the signals, compared to similar, but off-resonant excitation schemes. A simple explanation lies in the selectivity of Doppler classes. Our numerical simulations based on a four-level model including a whole Doppler ensemble can qualitatively describe the data.
Highlights
The field of quantum information processing by using Rydberg atoms has attracted intense interests due to the strong and long-range dipole–dipole interaction [2]
It has been proposed to make use of Rydberg atoms to realize a quantum repeater [8,9,10], which is an essential component for demonstrating long-distance quantum communication suffering from transmission loss [11]
The bichromatic excitation scheme involving long-lived Rydberg states can be superior to common lambda schemes connecting different hyperfine states by the mere frequency difference between pump and probe beams
Summary
The field of quantum information processing by using Rydberg atoms has attracted intense interests due to the strong and long-range dipole–dipole interaction [2]. It has been proposed to make use of Rydberg atoms to realize a quantum repeater [8,9,10], which is an essential component for demonstrating long-distance quantum communication suffering from transmission loss [11] Another important requirement for a quantum network is the ability to delay or even store quantum information for a certain time. Rydberg four-wave mixing (FWM) adds nonlinearities to the medium induced from the strong interaction between Rydberg atoms, and the FWM process can be used for creating the non-classical light fields These interactions have been discussed and experimentally demonstrated for the generation of single-photon sources [12,13,14] and the manipulation of quantum state [15,16,17]. By driving the transitions intensely and probing on timescales short compared to the movement of the atoms, the studies of the optical nonlinearities to singlephoton level can be extended to such systems [18, 19]
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