Optical vortex produced by Single Photon Subtraction from two mode   squeezed state Produces Maximum Entanglement
  In this article we report that the entanglement produced by single photon subtraction is maximum, by studying the entanglement of multi photon subtraction from two mode squeezed states. We argue that the single photon subtraction produces maximum entanglement as it is more non-classical in nature than many photon subtractions 
Abir Bandyopadhyay, Anindya Banerji and R. P. Singh
quant-ph physics.optics