  Properties and applications of a plasmonic cross-shaped nano-antenna is
presented and compared to those of array of holes. A simple analytical model
based on the superposition of waves are proposed and compared to the numerical
results. A direct consequence of unequal path for two orthogonal surface waves
leads to a coherent quantum interferometer with interesting properties.
Mechanism behind the rotating surface charge densities and consequently, the
formation of rotating resultant dipole moments is identified and the concept of
Dipole-SPP-LSP-Stokes coupling is introduced. All of which leads to the most
significant findings (a) foundation of a three-level quantum system for
entangled photons, based on the polarization states of the transmitted light
and (b) further encapsulation of the three-level quantum system into a
continuous orthonormal set of pure quantum states (c) an inference on the
nonexistence of spin in a single photon, hence the requirement of two photons
to create such spin states.
