Measurement of Nonlocal Variables without Breaking Causality
Abstract
We report results of an investigation of relativistic causality constraints on the measurability of nonlocal variables. We show that measurability of certain nondegenerate variables with entangled eigenstates contradicts the principle of causality, but that there are other, certainly nonlocal, variables which can be measured without breaking causality. We show that any causal measurement of nonlocal variables must erase certain local information. For example, for a system of two spin1/2 particles, even if we take the weakest possible definition of verification measurement, verification of an entangled state must erase all local information.
 Publication:

arXiv eprints
 Pub Date:
 June 1993
 arXiv:
 arXiv:hepth/9306086
 Bibcode:
 1993hep.th....6086V
 Keywords:

 High Energy Physics  Theory
 EPrint:
 6 pages, to be published in the Proceedings of "Fundamental Problems of Quantum Theory," Columbia SC 1992#