Tools for detecting entanglement between different degrees of freedom in   quadrature squeezed cylindrically polarized modes
  Quadrature squeezed cylindrically polarized modes contain entanglement not only in the polarization and spatial electric field variables but also between these two degrees of freedom [1]. In this paper we present tools to generate and detect this entanglement. Experimentally we demonstrate the generation of quadrature squeezing in cylindrically polarized modes by mode transforming a squeezed Gaussian mode. Specifically, -1.2 dB of amplitude squeezing are achieved in the radially and azimuthally polarized mode. Furthermore, theoretically it is shown how the entanglement contained within these modes can be measured and how strong the quantum correlations, depending on the measurement scheme, are. 
Christian Gabriel, Andrea Aiello, Stefan Berg-Johansen, Christoph   Marquardt and Gerd Leuchs
quant-ph