Quantum Information through Angular momentum of Photon
  The angular momentum of photons is the key source of quantum information. The transfer angular momentum is possible as circularly polarized light passed through wave plates. The twisted birefringent medium behaves as Q-plate. The passage of circularly polarized light through two consecutive half wave plates traces a closed curve on Poincare sphere. As a result the geometric phase in association with gain of orbital angular momentum is developed. 
Dipti Banerjee and Dipan Sinha
physics.optics