Single photon experiments and quantum complementarity.

Progress in Physics, April, 2007 by Georgiev, Danko Dimchev

Single photon experiments have been used as one of the most striking illustrations of the apparently nonclassical nature of the quantum world. In this review we examine the mathematical basis of the principle of complementarity and explain why the Englert-Greenberger duality relation is not violated in the configurations of Unruh and of Afshar.

Introduction

In classical physics if we have two distinct physical states [[psi].sub.1] [not equal to] [[psi].sub.2] of a physical system and we know that [[psi].sub.1] OR [[psi].sub.2] is a true statement we can easily deduce that [[psi].sub.1] XOR [[psi].sub.2] is a true statement too. In Quantum Mechanics however we encounter a novel possibility for quantum coherent superposition. It has been verified in...