We present the experimental demonstration of interaction induced enhancement in Rydberg excitation or Rydberg anti-blockade in thermal atomic vapor. We have used optical heterodyne detection technique to measure Rydberg population due to two-photon excitation to the Rydberg state. The anti-blockade peak which doesn’t satisfy the two-photon resonant condition is observed along with the usual two-photon resonant peak which can’t be explained using the model with non-interacting three-level atomic system. A model involving two interacting atoms is formulated for thermal atomic vapor using the dressed states of three-level atomic system to explain the experimental observations. A non-linear dependence of vapor density is observed for the anti-blockade peak which also increases with increase in principal quantum number of the Rydberg state. A good agreement is found between the experimental observations and the proposed interacting model. Our result implies possible applications towards quantum logic gates using Rydberg anti-blockade in thermal atomic vapor.

No abstract

We demonstrate a technique based on optical heterodyne detection to measure Rydberg population in thermal atomic vapour. The technique used a probe beam far off resonant to the D2 line of rubidium along with a reference beam with frequency offset by 800 MHz in the presence of a coupling laser that couples to Rydberg state via two-photon resonance. The polarizations of the probe, reference and coupling beams are suitably chosen such that only the probe beam goes through a non-linear phase shift due to two-photon process which is measured relative to the phase shift of the reference beam using optical heterodyne detection technique. We show that the technique has a sensitivity to measure the minimum phase shift of the order of few µrad. We have used a suitable model of two-photon excitation of a 3-level atom to show that the minimum phase shift measured in our experiment corresponds to Rydberg population of the order of 10 −5 . The corresponding probe absorption for the given laser parameters is of the order of 10 −7 . We demonstrate that this technique is insensitive to polarization impurity or fluctuations in the beams. The technique is particularly useful in measuring Rydberg population via two-photon excitation in thermal vapour where multi channel plates (MCP) could be relatively difficult to impliment. It can also be used in ultra-cold atomic sample with suitable laser parameters.

No abstract

No abstract