Transactional interpretation

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The transactional interpretation of quantum mechanics (TIQM) by John Cramer is an unusual interpretation of quantum mechanics that describes quantum interactions in terms of a standing wave formed by retarded (forward-in-time) and advanced (backward-in-time) waves. The author argues that it avoids the philosophical problems with the Copenhagen interpretation and the role of the observer, and resolves various quantum paradoxes. Notably, it is claimed to be consistent with Shahriar Afshar's experiment.

The existence of both advanced and retarded waves as lawful solutions to Maxwell's equations was proposed by R. Feynman and J. Wheeler in 1945 (cited in original paper by J. Cramer). They used the idea to solve the problem of the self-energy of an electron.

Cramer revived their idea of two waves to formulate his original interpretation of quantum theory. According to TIQM, any source emits a usual (retarded) wave of half the observed amplitude, while the detector emits a corresponding advanced wave of the same half amplitude. The phases of retarded and advanced waves are correlated in such a way that these two waves interfere positively in the space-time region, corresponding to true (observed) wave propagation, and they interfere negatively in all the other space-time (i.e., before emitting point and after absorption point). To an observer, this standing wave in space-time looks as if a particle has travelled through space.

Cramer uses TIQM in teaching quantum mechanics at the University of Washington in Seattle.

[edit] Literature

Tim Maudlin, Quantum Non-Locality and Relativity, Blackwell Publishers 2002, ISBN 0-631-23220-6 (discusses a gedanken experiment designed to refute the TI)