Operationalistic orthogonality condition for single-mode biphotons (qutrits)
Andrei A. Zhukov, Gleb Maslennikov, Maria V. Chekhova · Journal of Experimental and Theoretical Physics Letters · 2002
An arbitrary polarization state of a single-mode biphoton is considered. The operationalistic criterion is formulated for the orthogonality of these states. It can be used to separate a biphoton with an arbitrary degree of polarization from a set of biphotons orthogonal to it. This is necessary for the implementation of quantum cryptography protocol based on the three-level systems. The experimental test of this criterion amounts to the observation of the anticorrelation effect for a biphoton with an arbitrary polarization state.