Correlations of Rydberg excitations in an ultra-cold gas after an echo sequence

TL;DR

This paper demonstrates that an echo sequence can induce preferred nearest-neighbor correlations among Rydberg atoms in ultra-cold gases, resulting in non-Poissonian atom statistics and revealing new correlation dynamics.

Contribution

It introduces a novel echo sequence method to control Rydberg atom correlations and employs the omega-expansion for approximate dynamics analysis.

Findings

Atoms exhibit strong nearest-neighbor correlations after the echo sequence.

Atom counting statistics deviate significantly from Poissonian distribution.

The omega-expansion effectively describes correlation dynamics in the system.

Abstract

We show that Rydberg states in an ultra-cold gas can be excited with strongly preferred nearest-neighbor distance if densities are well below saturation. The scheme makes use of an echo sequence in which the first half of a laser pulse excites Rydberg states while the second half returns atoms to the ground state, as in the experiment of Raitzsch et al. [Phys. Rev. Lett. 100 (2008) 013002]. Near to the end of the echo sequence, almost any remaining Rydberg atom is separated from its next-neighbor Rydberg atom by a distance slightly larger than the instantaneous blockade radius half-way through the pulse. These correlations lead to large deviations of the atom counting statistics from a Poissonian distribution. Our results are based on the exact quantum evolution of samples with small numbers of atoms. We finally demonstrate the utility of the omega-expansion for the approximate description of correlation dynamics through an echo sequence.