Many-minds interpretation
While the mathematical structure has a strong foundation, there is still much debate about the physical and philosophical interpretation of the theory.
These interpretations aim to tackle various concepts such as: The standard solution to the measurement problem is the "Orthodox" or "Copenhagen" interpretation, which claims that the wave function collapses as the result of a measurement by an observer or apparatus external to the quantum system.
This includes observers and measurement systems, which become part of one universal state (the wavefunction) that is always described via the Schrödinger Equation (or its relativistic alternative).
For example, consider an observer measuring some particle that starts in an undetermined state, as both spin-up and spin-down, that is – a superposition of both possibilities.
Looking at the instrument informs the observer which branch he is on, but the system itself is indeterminate at this and, by logical extension, presumably any higher level.
There is no collapse of the wavefunction into one state or another, but rather an observer finds itself in the world leading up to what measurement it has made and is unaware of the other possibilities that are equally real.
The many-minds interpretation of quantum theory is many-worlds with the distinction between worlds constructed at the level of the individual observer.
However, the observer's mind seeing one result does not directly affect the distant state – there is just no wave function in which the expected correlations do not exist.
The correlations on the level of individual minds correspond to the appearance of quantum non-locality (or equivalently, violation of Bell's inequality).
In light of Bell's analysis of the consequences of quantum non-locality, empirical evidence is needed to avoid inventing novel fundamental concepts (hidden variables).
[9] Two different solutions of the measurement problem then appear conceivable: von Neumann's collapse or Everett's relative state interpretation.
Speculation about the details of this awareness-local physical system coupling on a purely theoretical basis could occur, however experimentally searching for them through neurological and psychological studies would be ideal.
[11] Nothing within quantum theory itself requires each possibility within a wave function to complement a mental state.
[citation needed] Albert and Loewer argue that the mind must be intrinsically different than the physical reality as described by quantum theory.
[12] Another serious objection is that workers in no collapse interpretations have produced no more than elementary models based on the definite existence of specific measuring devices.
They have assumed, for example, that the Hilbert space of the universe splits naturally into a tensor product structure compatible with the measurement under consideration.
[13] Peter J. Lewis argues that the many-minds interpretation of quantum mechanics has absurd implications for agents facing life-or-death decisions.
Moreover, the theory advises one to favour choices in such situations in proportion to the probability that they will bring good results to one's various successors.
So it seems that the many-minds interpretation advises one to get in the box with the cat, since it is certain that one's only successor will emerge unharmed.
