Bell's Theorem and Spacetime-Based Reformulations of Quantum Mechanics. (arXiv:1906.04313v1 [quant-ph])

In this critical review of Bell's Theorem, its implications for
reformulations of quantum theory are considered. The assumptions of the theorem
are set out explicitly, within a framework of mathematical models with
well-defined inputs and outputs. Attention is drawn to the assumption that the
mathematical quantities associated with a certain time and place can depend on
past model inputs (such as preparation settings) but not on future inputs (such
as measurement settings at later times). Keeping this time-asymmetric
assumption leads to a substantial tension between quantum mechanics and
relativity. Relaxing it, as should be considered for such no-go theorems, opens
a category of Future-Input Dependent (FID) models, for which this tension need
not occur. This option (often called `retrocausal') has been repeatedly pointed
out in the literature, but the exploration of explicit FID models capable of
describing specific entanglement phenomena has begun only in the past decade. A
brief survey of such models is included here. Unlike conventional quantum
models, the FID model parameters needed to specify the state of a system do not
grow exponentially with the number of entangled particles. The promise of
generalizing FID models into a Lorentz-covariant account of all quantum
phenomena is identified as a grand challenge.

Article web page: