# Entangled pulses of 105 photons

## Newsletter 6

Recently we have produced bright pulses, each containing 10^{5} photons, that manifest macroscopic entanglement. Although the photons emitted into beams A and B are randomly polarised, their polarisation states are strictly correlated. This means that the number of photons in any polarization mode of beam A is exactly equal to the number of orthogonally polarised photons in beam B. To verify this entanglement, we used a simple criterion: for a separable (non-entangled) state, the sum of the variances for three Stokes observables normalized to the mean photon number cannot be less than 2. The measurement, performed jointly on beams A and B, shows violation of this condition by more than five standard deviations and thus confirms entanglement. The violation occurs only in a certain range of the diameter D1 of an aperture providing proper mode matching between beams A and B.

**Contact: **maria.chekhova(at)mpl.mpg(dot)de**Group:** *Single Photon Technology (TDSU)***Reference:** T. Sh. Iskhakov et al., Phys. Rev. Lett. **109**, 150502 (2012).