  We present experimental demonstration of quadrature and polarization
entanglement generated via the interaction between a coherent linearly
polarized field and cold atoms in a high finesse optical cavity. The non linear
atom-field interaction produces two squeezed modes with orthogonal
polarizations which are used to generate a pair of non separable beams, the
entanglement of which is demonstrated by checking the inseparability criterion
for continuous variables recently derived by Duan et al. [Phys. Rev. Lett. 84,
2722 (2000)] and calculating the entanglement of formation [Giedke et al.,
Phys. Rev. Lett. 91, 107901 (2003)].

Quantum Physics