München 2009 – scientific programme

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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 5: Quantentheorie

AGPhil 5.1: Talk

Wednesday, March 11, 2009, 16:45–17:15, M014

Quantum Completeness and Consistent Histories — •Carsten Held — Universität Erfurt

The different versions of the Kochen-Specker Theorem show that quantum mechanics (QM) cannot be supplemented by hidden variables given two plausible constraints. This collection of results is generally interpreted as showing that QM is complete in the following way. Consider that a QM system's state allows calculating probabilities for the possession of values of observables. Then the system has only those values for which the state delivers probability 1. For a positive probability different from 1 the system is then thought to adopt a value as a result of the measurement interaction. But this interpretation is fundamentally problematic. In particular, it can be easily brought into contradiction with QM itself, given two very general principles concerning probabilities in a physical theory. This difficulty which may be called the completeness problem is seldom noticed. A notable exception is the consistent histories interpretation (CHI) of QM. The CHI points out the problem and proposes a solution. Here I investigate the proposal. I argue that the CHI can avoid contradiction only at the cost of distorting the original sense of the completeness assumption and prohibiting the hidden-variables question itself. Hence, its attempt to overcome the problem is implausible.