The correlations in the properties of the two quantum systems in the figure can be too strong to be explained by their independent evolution from the initial condition. They cannot influence each other through the grey areas, so an explanation is the final boundary condition.

There are two broad approaches to a theory of time. In the A-theory or “dynamic” view, the past and future have different status and usually the present is thought of as moving forwards as the future changes into the past. In the B-theory or “static” or block universe view, the past and future have similar status and the present is not necessarily a privileged element in the structure of spacetime. Our human experience strongly favours A-theory but it is generally accepted that modern physics favours B-theory. Gödel, for example, considered that he had proved that the B-theory view is correct.

On the B-theory, time does not “flow”, the future is fixed and one would expect final boundary conditions (FBC’s) to be as important as initial boundary conditions (IBC’s). Any phenomena directly dependent on the FBC’s would appear to be inexplicable in terms of a physical theory (wrongly!) formulated in terms of IBC’s only. There are no such phenomena in classical physics (which can be formulated either in terms of IBC’s alone or both IBC’s and FBC’s) but there are in quantum physics.

A notorious example is the “measurement problem” in which the quantum system and measuring instrument ought to end up in a superposition of states. The fact that we observe a single state is inexplicable in terms of standard quantum mechanics which has to be amended by the inclusion of a postulate: what von Neumann called Process One. (An alternative to that is to adopt the “relative state” view in which we are indeed in a superposition of states but don’t know it.)

The better approach, not requiring an additional postulate, is to realise that the uniqueness of measurement outcomes only appears to be inexplicable because it is in fact a manifestation of the FBC’s. I have justified this by showing that sufficiently complicated phenomena like measurement outcomes are expected to be uniquely determined by the FBC’s in quantum mechanics.

Another example is the correlations of properties among entangled quantum systems - they are too strong (Bell’s inequalities) to be explained by the IBC’s without what Einstein called “spooky” action-at-a-distance. On our view, the unmeasured properties of the quantum systems are not correlated but any measured properties of them are because of the FBC’s. In short, a perfectly satisfactory and natural explanation of all the “quantum mysteries” is to be found in the B-theory of time.

David Miller