Realization of the Einstein-Podolsky-Rosen Paradox Using Momentum- and Position-Entangled Photons from Spontaneous Parametric Down Conversion

We report on a momentum-position realization of the EPR paradox using direct detection in the near and far fields of the photons emitted by collinear type-II phase-matched parametric down conversion. Using this approach we achieved a measured two-photon momentum-position variance product of $0.01{\hslash }^2$, which dramatically violates the bounds for the EPR and separability criteria.

Figure 1

Experimental setup for measuring photon correlations. (a) Position correlations are obtained by imaging the birthplace of each photon of a pair onto a separate detector. (b) Correlations in transverse momentum are obtained by imaging the propagation direction of each photon of a pair onto a separate detector.

Figure 2

(a) The conditional probability distribution of the relative birthplace of the entangled photons. (b) The conditional probability distribution of the relative transverse momentum of the entangled photons. The widths of the distributions determine the uncertainties in inferring the position or the momentum of one photon from that of the other. The solid lines are the theoretical predictions and the dots are the experimental data.