Annotated Bibliography Part 1

1. DeWitt, B. (1970) “Quantum Mechanics and Reality.” Physics Today, 32-34

Summary

The article talks of the initial shock of being confronted with the Many-Worlds Interpretation (MWI) of quantum mechanics, which suggests that an overwhelmingly vast number of very slightly different copies of oneself perpetually branch out into new versions. The idea is difficult to reconcile with ordinary sense and therefore comes across as much more extreme than in Wigner’s Friend thought experiment, where only one observer hovers between two possibilities. The point of the passage is that even if we are unable to see ourselves splitting up into duplicates, it is only because as physical systems we will be acting like automata. Quantum mechanical rules will not allow us to “experience” branching. To support this argument, the passage illustrates a thought experiment involving two measurement devices. The first measures the outcome of a quantum measurement, and the second checks both the first device’s memory and the observable itself. If the Many-Worlds Interpretation is true, then each branch of the wave function will be self-consistent—both devices must confirm the result observed. This is proven by the results, as the measurements in every branch are all equal to one another. So, although the branching occurs, it is invisible to any one observer.

 

 

1.  Everett, H.(1957). “Relative State Formulation of Quantum Mechanics.” Physics, 29, 454

Summary

Hugh Everett’s description of quantum mechanics differs from the conventional collapse formulation and Copenhagen interpretation by highlighting their inconsistency with describing nested measurements, as in the Wigner’s Friend thought experiment. Everett proposed that pure wave mechanics is a consistent description of the evolution of composite systems without wave function collapse. Everett’s relative-state formulation has several advantages. It abolishes the need for collapse dynamics, thereby disposing of contradictions within the standard theory. It is also logically sound, universally applicable, and maximally simple in being empirically correct. Within this interpretation, measurement record sequences that agree with standard quantum statistics occur naturally. However, the relative-state formalism is deficient empirically. It has no provision to predict probabilistically an individual record of a measurement at some future or present moment in time. As a reaction, modern reinterpretations of pure wave mechanics impose conditions to account for determinate records and quantum probability without disturbing the original theoretical setup as little as possible.