What Quantum Measurements Measure

Tuesday, December 6, 2016 - 12:00pm to 1:00pm
Cathedral of Learning 817

Discussions of the infamous measurement problem of quantum foundations tend to focus on how the output of a measurement, the pointer position, can be thought of in consistent quantum mechanical terms, while ignoring the equally important issue of what this outcome says about the earlier microscopic situation the apparatus was designed to measure. An experimental physicist is typically much more interested in the path followed by a particle before it triggered his detector than in what happened later, and if quantum mechanics cannot provide a clear explanation, how can one claim that this theory has been confirmed by experiment? The talk will use Wheeler's delayed choice paradox to identify the fundamental conceptual issues underlying this second measurement problem, and then sketch the resolution provided by the consistent histories interpretation, using a modification of Birkhoff and von Neumann's quantum logic.