Cosmic quantum measurement

Abstract

Hardy's theorem states that the hidden variables of any realistic theory of quantum measurement, whose predictions agree with ordinary quantum theory, must have a preferred Lorentz frame. This presents the conflict between special relativity and any realistic dynamics of quantum measurement in a severe form. The conflict is resolved using a `measurement field', which provides a timelike function of spacetime points and a definition of simultaneity in the context of a curved spacetime. Locally this theory is consistent with special relativity, but globally, special relativity is not enough; the time dilation of general relativity and the standard cosmic time of the Robertson-Walker cosmologies are both essential. A simple but crude example is a relativistic quantum measurement dynamics based on the nonrelativistic measurement dynamics of L\"uders.