Entanglement propagation of a quantum optical vortex state

• We study entanglement evolution of quantum optical vortex in coupled lossless waveguides.
• We compare results for two methods of generation of quantum optical vortex.
• The associated Wigner function exhibits interesting quantum interference pattern.
• Decay and subsequent regeneration of entanglement is observed.

We study the entanglement evolution of a quantum optical vortex state propagating through coupled lossless waveguides. We consider states generated by coupling two squeezed modes using a sequence of beam splitters and also by subtracting photons from one of the output modes in spontaneous parametric down conversion. We use the Wigner function to study the variation in the structure of the vortex state with distance and quantify the entanglement after propagation using logarithmic negativity.