Roger Colbeck (ETH Zurich), Institute for Quantum Computing (IQC)
Abstract
According to quantum theory, measurements generate random outcomes, in stark contrast with classical mechanics. This raises the important question of whether there could exist an extension of the theory which removes this indeterminism, as famously suspected by Einstein, Podolsky and Rosen. Under the assumption of free choice within a particular causal structure, Bell's work showed this to be impossible. However, existing results do not imply that the current theory is maximally informative. Could it be that certain hidden variable theories (for example) allow us to make more accurate predictions about the outcomes?
In this talk, I will discuss this question and show that, under the same free choice assumption, the answer is negative: no extension of quantum theory can give more information about the outcomes of future measurements than quantum theory itself.
I will then show that as a corollary of this result, we can reach the same conclusion as Pusey, Barrett and Rudolph that the wavefunction cannot be thought of as subjective.
(This is based on arXiv:1005.5173, arXiv:1111.6597 and arXiv:1208.4123)