Correlated Photon Emission from Multiatom Rydberg Dark States

We consider three-level atoms driven by two resonant light fields in a ladder scheme where the upper level is a highly excited Rydberg state. We show that the dipole-dipole interactions between Rydberg excited atoms prevents the formation of single particle dark states and leads to strongly correlated photon pairs from atoms separated by distances large compared to the emission wavelength. For a pair of atoms, this enables realization of an efficient photon-pair source with on average one pair every $30\mu \mathrm{s}$.

Figure 1

(a) Schematic of a few-atom system confined within a sphere radius $R<R_b$. The dipole blockade modifies the EIT dark state created by the probe and coupling lasers, leading to strongly correlated photon-pair emission that can be efficiently collected and measured using detectors $D_1$ and $D_2$. (b) Level-scheme for two-atoms with a dipole-dipole coupling $V(R)$ between the Rydberg states, where $R$ is the interatomic separation.

Figure 2

$\mathcal{N}$-atom fluorescence correlations. (a) Independent two-level atoms for ${\Omega }_p={\Gamma }_e/5$ displaying antibunching. (b)–(d) interacting EIT system with ${\Omega }_c={\Gamma }_e$, $V(r_{ij})=2{\Gamma }_e$ and ${\Omega }_p={\Gamma }_e/5$, ${\Gamma }_e/2$, and ${\Gamma }_e$ respectively.

Figure 3

Self- and cross-correlations in emsission from two distinguishable atoms. (a) ${\Omega }_p={\Gamma }_e/5$. Two-level atoms have an independent cross-correlation as the atoms are noninteracting. (b)–(d) Interacting EIT system with ${\Omega }_c={\Gamma }_e$, $V(r_{ij})=2{\Gamma }_e$ and ${\Omega }_p={\Gamma }_e/5$, ${\Gamma }_e/2$, and ${\Gamma }_e$ respectively. This shows the bunching arises from the strong cross-correlation between the atoms, which are correlated by the dipole blockade.

Figure 4

Correlation function for coherent emission for different separations $R$, where $m$ is an integer. (a) Atoms aligned parallel to the probe beam are bunched for all separations. (b) The perpendicular configuration shows antibunching due to destructive interference for $R=m\lambda +\lambda /4$, $3\lambda /4$.