Chapter 4: EPR Pair and Measurement

In the 1920s when quantum mechanics was being established, there was a famous controversy between Bohr and Einstein about the statistical interpretation of quantum mechanics. The controversy was finally concluded by an emphatic victory of Bohr, since his statistical interpretation and the duality of wave and particle explained many experimental facts without any difficulty. The “Gedanken” experiment on two entangled particles (the EPR pair) presented by Einstein, Podolski and Rosen in the course of the controversy, however, has had a continuous influence for many years on quantum communication and quantum cryptography which are being developed at the present day.