Minkowski Institute, 21.03.2016
In an interesting recent publication (Mahler et al., Science Advances, 19 Feb 2016, Vol. 2, no. 2) Aephraim Steinberg (University of Toronto) and collaborators perform a remarkable double-slit experiment on entangled photons, measuring trajectories that some have termed “surreal”. They claim that “the trajectories seem surreal only if one ignores their manifest nonlocality”.
However one should be careful about what type of nonlocality one speaks of. I do not see where the experiment points to non-locality in the strong sense of superluminal interactions. I believe the measured effects of entanglement can be explained by long-range correlations – which also exist in countless classical systems. For instance, in recently discovered fluid-mechanical systems involving oil droplets bouncing on a vibrating oil film (and mimicking a wide range of quantum phenomena), these correlations exist (cf. http://link.springer.com/article/10.1007%2Fs10701-015-9973-7). Such correlations are long-range or ‘delocalized’ but not non-local in the strong sense.
The Steinberg experiments do however give credit to de Broglie – Bohm theory, since this is the most natural theory to calculate trajectories (which in principle do not exist according to Copenhagen). It is usually believed Bohm’s theory is nonlocal because if one changes a boundary condition somewhere in the universe, the quantum potential (based on the wave function) ‘instantaneously changes’. But in exactly the same mathematical way, if you change the boundary conditions of a fluid somewhere, the ‘fluid field solutions instantaneously differ’. de Broglie – Bohm theory is not more non-local than fluid mechanics (cf. some ideas here: http://philpapers.org/archive/VERMOD.pdf). A common denominator between de Broglie’s theory and the droplet experiments is the existence of some kind of background field (quantum vacuum, ether or surface wave). Such a background presenting long-range correlations can indeed explain the Bell experiment in a local manner, it seems: cf. http://link.springer.com/article/10.1007%2Fs10701-015-9973-7.
In all the above you don’t need nonlocality in the strong sense. Therefore I prefer Bohm’s term ‘quantum wholeness’, which does not overtly violate relativity theory.