Interference and distinguishability

Jos Uffink and Jan Hilgevoord, Institute for History and Foundations of Science, Utrecht University (NL).

This article is available from the quant-ph archive in Los Alamos.

Quantitative measures are introduced for the indistinguishability $U$ of two quantum states in a given measurement and the amount of interference $I$ observable in this measurement. It is shown that these measures obey an inequality $U\geq I$ which can be seen as an exact formulation of Bohr's claim that one cannot distinguish between two possible paths of a particle while maintaining an interference phenomenon. This formulation is applied to a neutron interferometer experiment of Badurek e.a. It is shown that the formulation is stronger than an argument based on an uncertainty relation for phase and photon number considered by these authors.

Last updated: Friday, 30-Jun-2000 15:24:00 CEST