Higher order nonclassicalities in a codirectional nonlinear optical   coupler: Quantum entanglement, squeezing and antibunching
  Higher order nonclassical properties of fields propagating through a codirectional asymmetric nonlinear optical coupler which is prepared by combining a linear wave guide and a nonlinear (quadratic) wave guide operated by second harmonic generation are studied. A completely quantum mechanical description is used here to describe the system. Closed form analytic solutions of Heisenberg's equations of motion for various modes are used to show the existence of higher order antibunching, higher order squeezing, higher order two-mode and multi-mode entanglement in the asymmetric nonlinear optical coupler. It is also shown that nonclassical properties of light can transfer from a nonlinear wave guide to a linear wave guide. 
Kishore Thapliyal, Anirban Pathak, Biswajit Sen, and Jan Perina
quant-ph physics.optics