NONLOCAL CHARACTER OF QUANTUM-THEORY

According to a common conception of causality, the truth of a statemen t that refers only to phenomena confined to an earlier time cannot dep end upon which measurement an experimenter will freely choose to perfo rm at a later time. According to a common idea of the theory of relati vity this causality condition should be valid in all Lorentz frames. I t is shown here that this concept of relativistic causality is incompa tible with some simple predictions of quantum theory. (C) 1997 America n Association of Physics Teachers.