Sutherland's latest paper on entanglement as local retrocausality
JACK SARFATTI
re: http://aip.scitation.org/toc/apc/1841/1?expanded=1841
Roderick I. Sutherland
Centre for Time, University of Sydney, NSW 2006 Australia
rod.sut...@sydney.edu.au
It has become increasingly apparent that a number of perplexing issues associated with the interpretation of quantum mechanics are more easily resolved once the notion of retrocausality is introduced. The aim here is to list and discuss various examples where a clear explanation has become available via this approach. In so doing, the intention is to highlight that this direction of research deserves more attention than it presently receives.
Introduction
While quantum mechanics is a highly successful mathematical theory in terms of experimental verification, there remain long-standing questions as to what sort of physical reality could be underlying the mathematics and giving rise to the theory’s stranger predictions. Unlike classical mechanics, the theory does not give sufficient guidance towards identifying the appropriate ontology. Over time, there has been a growing awareness that backwards-in-time influences, or retrocausality, might be relevant in interpreting and understanding some of the phenomena in question. The intention here is to summarise some of the advantages that can be gained by introducing retrocausality into the underlying picture. In particular, it is found that taking this step can achieve the following:
It can restore locality in the case of entangled states (such as with Bell’s theorem)
It can preserve consistency with special relativity at the ontological level
It can allow replacement of many-particle, configuration space wavefunctions by
individual wavefunctions
In can allow statistical descriptions to be replaced by definite, ontological values
It can facilitate the development of a Lagrangian formulation in the case where a
particle ontology is assumed
It can suggest significant improvements to existing ontological models.
These points will be discussed individually in the following sections. A first step, however, is to define more precisely what is meant by retrocausality here. In doing so, it should be noted that no suggestion is being made of movement through 4-dimensional spacetime in either the forwards or backwards time directions. Motion remains confined, as usual, to the 3-dimensional picture. In this context, the definition of retrocausality will be taken to be as follows:
It is necessary to specify final boundary conditions as well as the usual initial ones in order to determine the state completely at any intermediate time, with the experimenter’s controllable choice of the final conditions thereby exerting a backwards-in-time influence.
For further clarity, two conventions will be introduced at this point:
(i) Since any initial boundary condition in standard quantum mechanics is specified by a
Hilbert space vector i , it will be presumed by symmetry that any final boundary condition
should be similarly specified by a Hilbert space vector
f .
(ii) The initial boundary condition here will simply be equated with the result of the most recent prior measurement performed on the system. Similarly, any final boundary condition will be equated with the result of the next measurement performed. (This is not intended to imply any special status for measurement interactions compared with other interactions, but merely to frame the discussion in a clear-cut form.)
These two conventions keep the mathematics simple and straightforward. Using the second one, the definition of retrocausality can be formulated more specifically as:
The choice of observable measured at a particular time can affect the state existing at an earlier time.
Having defined retrocausality in this way, various advantages it provides will now be discussed.