Interpretation of quantum mechanics

Quantum mechanics as a physical theory has been very successful in predicting experimental results. However it becomes philosophically troublesome once it is mathematically demonstrated that it cannot have all of the properties that one would inituitively expect for it to have.

One intuitively would like a physical theory

  • That is complete and not requiring any outside theory;
  • that is local in that the events at one point are only affected by nearby areas;
  • that is deterministic: given one set of circumstances, there is only one possible outcome;
  • that requires no further "hidden" variables to determine this outcome;
  • that predicts only one universe.

However, Bell's theorem appears to prevent quantum mechanics from having all of these properties. Whether or not the real world is local and deterministic is another matter. The possiblity that quantum mechanics is simply wrong has still not been completely ruled out by the Bell test experiments.

At first glance all of the interpretations of quantum mechanics appear to produce the same physical results, which makes distinguishing between them on the basis of experiment to be impossible. Nevertheless, there is active research in attempting to come up with experimental tests which would allow differences between the interpretations to be experimentally tested.


Some of the most common interpretations are summarized here:

Interpretation Deterministic? Waveform real? One
Universe?		 Avoids
hidden variables?		 Local? Avoids
collapsing wavefunctions?
Copenhagen interpretation
(Waveform not real)		 No No Yes Yes No Yes
Copenhagen interpretation
(Waveform real)		 No Yes Yes Yes No No
Consistent Histories No No Yes Yes Yes Yes
Consciousness causes Collapse No Yes Yes Yes No No
Everett many-worlds interpretation Yes Yes No Yes* Yes Yes
Bohm interpretation Yes No Yes No No Yes

*Many Worlds has no hidden variables, except for the multiple worlds themselves.

Each interpretation has many variants. It is very difficult to get a precise definition of the Copenhagen Interpretation — in the table above, two variants of the Copenhagen Interpretation are shown — one that regards the waveform as being a tool for calculating probabilties only, and the other regards the waveform as an "element of reality".


See also

List of physics topics : Quantum mechanics, Quantum indeterminacy, Bell's theorem, Bohm interpretation, Copenhagen interpretation, Many-worlds interpretation, Wavefunction collapse, Measurement problem, Quantum computation, Unsolved problems in physics

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