Interpretations of Quantum Mechanics - Comparison of Interpretations

Comparison of Interpretations

The most common interpretations are summarized in the table below. The values shown in the cells of the table are not without controversy, for the precise meanings of some of the concepts involved are unclear and, in fact, are themselves at the center of the controversy surrounding the given interpretation.

No experimental evidence exists that distinguishes among these interpretations. To that extent, the physical theory stands, and is consistent with itself and with reality; difficulties arise only when one attempts to "interpret" the theory. Nevertheless, designing experiments which would test the various interpretations is the subject of active research.

Most of these interpretations have variants. For example, it is difficult to get a precise definition of the Copenhagen interpretation as it was developed and argued about by many people.

Interpretation	Author(s)	Deterministic?	Wavefunction real?	Unique history?	Hidden variables?	Collapsing wavefunctions?	Observer role?	Local?	Counterfactual definiteness?
Ensemble interpretation	Max Born, 1926	Agnostic	No	Yes	Agnostic	No	None	No	No
Copenhagen interpretation	Niels Bohr, Werner Heisenberg, 1927	No	No1	Yes	No	Yes2	Causal	No	No
de Broglie–Bohm theory	Louis de Broglie, 1927, David Bohm, 1952	Yes	Yes3	Yes4	Yes	No	None	No	Yes
von Neumann interpretation	von Neumann, 1932, Wheeler, Wigner	No	Yes	Yes	No	Yes	Causal	No	No
Quantum logic	Garrett Birkhoff, 1936	Agnostic	Agnostic	Yes5	No	No	Interpretational6	Agnostic	No
Many-worlds interpretation	Hugh Everett, 1957	Yes	Yes	No	No	No	None	Yes	No
Popper's interpretation	Karl Popper, 1957	No	Yes	Yes	Yes	No	None	Yes	Yes13
Time-symmetric theories	Yakir Aharonov, 1964	Yes	Yes	Yes	Yes	No	No	Yes	No
Stochastic interpretation	Edward Nelson, 1966	No	No	Yes	No	No	None	No	No
Many-minds interpretation	H. Dieter Zeh, 1970	Yes	Yes	No	No	No	Interpretational7	Yes	No
Consistent histories	Robert B. Griffiths, 1984	Agnostic8	Agnostic8	No	No	No	Interpretational6	Yes	No
Objective collapse theories	Ghirardi–Rimini–Weber, 1986, Penrose interpretation, 1989	No	Yes	Yes	No	Yes	None	No	No
Transactional interpretation	John G. Cramer, 1986	No	Yes	Yes	No	Yes9	None	No	Yes14
Relational interpretation	Carlo Rovelli, 1994	No	No	Agnostic10	No	Yes11	Intrinsic12	Yes	No

1 According to Bohr, the concept of a physical state independent of the conditions of its experimental observation does not have a well-defined meaning. According to Heisenberg the wavefunction represents a probability, but not an objective reality itself in space and time.
2 According to the Copenhagen interpretation, the wavefunction collapses when a measurement is performed.
3 Both particle guiding wavefunction are real.
4 Unique particle history, but multiple wave histories.
5 But quantum logic is more limited in applicability than Coherent Histories.
6 Quantum mechanics is regarded as a way of predicting observations, or a theory of measurement.
7 Observers separate the universal wavefunction into orthogonal sets of experiences.
8 If wavefunction is real then this becomes the many-worlds interpretation. If wavefunction less than real, but more than just information, then Zurek calls this the "existential interpretation".
9 In the TI the collapse of the state vector is interpreted as the completion of the transaction between emitter and absorber.
10 Comparing histories between systems in this interpretation has no well-defined meaning.
11 Any physical interaction is treated as a collapse event relative to the systems involved, not just macroscopic or conscious observers.
12 The state of the system is observer-dependent, i.e., the state is specific to the reference frame of the observer.
13 Caused by the fact that Popper holds both CFD and locality to be true, it is under dispute whether Popper's interpretation can really be considered an interpretation of Quantum Mechanics (which is what Popper claimed) or whether it must be considered a modification of Quantum Mechanics (which is what many Physicists claim), and, in case of the latter, if this modification has been empirically refuted or not. Popper exchanged many long letters with Einstein, Bell etc. about the issue.
14 The transactional interpretation is explicitly non-local.

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