Tri-state Entanglement - Quantum cryptography is generally based on the entanglement of two photons that exist in a superposition of two quantum logic states, and rely on measurements of their polarization. In an article in Phys Rev. Lett. entitled "Experimental Two-Photon, Three-Dimensional Entanglement for Quantum Communication", the authors describe the preparing of entangled photons in a superposition of many different angular momentum states in order to increase the amount of quantum information transmitted by the photons could be increased. They (Alipasha Vaziri, Gregor Weihs, and Anton Zeilinger) claim such an arrangement is demonstrated by generating entangled photon pairs in a superposition of three orthogonal angular momentum states.