New Slant on the EPR-Bell Experiment

Abstract

The best case for thinking that quantum mechanics is nonlocal rests on Bell's Theorem, and later results of the same kind. However, the correlations characteristic of EPR-Bell (EPRB) experiments also arise in familiar cases elsewhere in QM, where the two measurements involved are timelike rather than spacelike separated; and in which the correlations are usually assumed to have a local causal explanation, requiring no action-ata-distance. It is interesting to ask how this is possible, in the light of Bell's Theorem. We investigate this question, and present two options. Either (i) the new cases are nonlocal, too, in which case action-at-a-distance is more widespread in QM than has previously been appreciated (and does not depend on entanglement, as usually construed); or (ii) the means of avoiding action-at-a-distance in the new cases extends in a natural way to EPRB, removing action-at-a-distance in these cases, too. There is a third option, viz., that the new cases are strongly disanalogous to EPRB. But this option requires an argument, so far missing, that the physical world breaks the symmetries which otherwise support the analogy. In the absence of such an argument, the orthodox combination of viewsaction-at-a-distance in EPRB, but local causality in its timelike analogue -is less well established than it is usually assumed to be. "Our intuition, going back forever, is that to move, say, a rock, one has to touch that rock, or touch a stick that touches the rock, or give an order that travels via vibrations through the air to the ear of a man with a stick that can then push the rock-or some such sequence. This intuition, more generally, is that things can only directly affect other things that are right next to them. If A affects B without being right next to it, then the effect in question must be indirect-the effect in question must be something that gets transmitted by means of a chain of events in which each event brings about the next one directly, in a manner that smoothly spans the distance from A to B. . . .We term this intuition 'locality.' Quantum mechanics has upended many an intuition, but none deeper than this one. And this particular upending carries with it a threat, as yet unresolved, to special relativity-a foundation stone of our 21st-century physics." ([1], p. 32.) 1 See, e.g., [36] and [10] for the former viewpoint, and [17] for an introduction to the latter.

Towards a formulation of quantum theory as a causally neutral theory of Bayesian inference

“…There are some clues that this might be possible. Several authors have noted that there are close connections, and often isomorphisms, between the statistics that can be obtained from quantum experiments with distinct causal arrangements [2][3][4][5][6][7][8]. Timereversal symmetry is an example of this, but it is also possible to relate experiments involving two systems at the same time with those involving a single system at two times.…”

Interpreting Quantum Theory

“…85. An analogous double standard in the orthodox view of the EPR-scenario has recently been pointed out along different lines in (Evans et al [2013]). …”

Causal Decision Theory and EPR correlations

“…Bell (1977) calls it the free will assumption, and e.g. Evans, Price & Wharton (2013) call it the no retrocausality assumption. We will not enter into the justification of these names, but it will be helpful to us to group the alternative glosses into two sub-options.…”