Many-minds interpretation

The many-minds interpretation of quantum mechanics extends the many-worlds interpretation by proposing that the distinction between worlds should be made at the level of the mind of an individual observer. The concept was first introduced in 1970 by H. Dieter Zeh as a variant of the Hugh Everett interpretation in connection with quantum decoherence, and later (in 1981) explicitly called a many or multi-consciousness interpretation. The name many-minds interpretation was first used by David Albert and Barry Loewer in 1988.

History

Interpretations of quantum mechanics

The various interpretations of quantum mechanics typically involve explaining the mathematical formalism of quantum mechanics, or to create a physical picture of the theory. 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:

Evolution of the state of a quantum system (given by the wavefunction), typically through the use of the Schrödinger equation. This concept is almost universally accepted, and is rarely put to debate.
The measurement problem, which relates to what is called wavefunction collapse – the collapse of a quantum state into a definite measurement (i.e. a specific eigenstate of the wavefunction). The debate on whether this collapse actually occurs is a central problem in interpreting quantum mechanics.

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. An alternative interpretation, the Many-worlds Interpretation, was first described by Hugh Everett in 1957 (where it was called the relative state interpretation, the name Many-worlds was coined by Bryce Seligman DeWitt starting in the 1960s and finalized in the 1970s). His formalism of quantum mechanics denied that a measurement requires a wave collapse, instead suggesting that all that is truly necessary of a measurement is that a quantum connection is formed between the particle, the measuring device, and the observer.

Non-locality of the many-minds interpretation

As we have thus seen, any correlations seen in the wavefunction of each observer's minds are only concrete after interaction between the different polarizers. The correlations on the level of individual minds correspond to the appearance of quantum non-locality (or equivalently, violation of Bell's inequality). So the many world is non-local, or it cannot explain EPR-GHZ correlations.

Support

There is currently no empirical evidence for the many-minds interpretation. However, there are theories that do not discredit the many-minds interpretation. 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). Two different solutions of the measurement problem then appear conceivable: consciousness causes collapse or Everett's relative state interpretation. In both cases a (suitably modified) psycho-physical parallelism can be re-established.

If neural processes can be described and analyzed then some experiments could potentially be created to test whether affecting neural processes can have an effect on a quantum system. 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.

Objections

Nothing within quantum theory itself requires each possibility within a wave function to complement a mental state. As all physical states (i.e. brain states) are quantum states, their associated mental states should be also. Nonetheless, it is not what one experiences within physical reality. Albert and Loewer argue that the mind must be intrinsically different than the physical reality as described by quantum theory. Thereby, they reject type-identity physicalism in favour of a non-reductive stance. However, Lockwood saves materialism through the notion of supervenience of the mental on the physical.

Nonetheless, the many-minds interpretation does not solve the mindless hulks problem as a problem of supervenience. Mental states do not supervene on brain states as a given brain state is compatible with different configurations of mental states.

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. They have also assumed, even when describing the behaviour of macroscopic objects, that it is appropriate to employ models in which only a few dimensions of Hilbert space are used to describe all the relevant behaviour.

Furthermore, as the many-minds interpretation is corroborated by our experience of physical reality, a notion of many unseen worlds and its compatibility with other physical theories (i.e. the principle of the conservation of mass) is difficult to reconcile.

Peter J. Lewis argues that the many-minds interpretation of quantum mechanics has absurd implications for agents facing life-or-death decisions.

In general, the many-minds theory holds that a conscious being who observes the outcome of a random zero-sum experiment will evolve into two successors in different observer states, each of whom observes one of the possible outcomes. 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. But in a life-or-death case like an observer getting into the box with Schrödinger's cat, the observer will only have one successor, since one of the outcomes will ensure the observers death. 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. See also quantum suicide and immortality.

Finally, it supposes that there is some physical distinction between a conscious observer and a non-conscious measuring device, so it seems to require eliminating the strong Church–Turing hypothesis or postulating a physical model for consciousness.

References

External links

Wikibook on consciousness
Bibliography on the Many-minds interpretation