## "Relative State" Formulation of Quantum Mechanics

* “From the viewpoint of the theory, all elements of a superposition (all ‘branches’) are ‘actual,’ none any more ‘real’ than the rest...” Hugh Everett*

FIRST EDITION IN ORIGINAL WRAPPERS of Hugh Everett's ground breaking work on the existence of multiple universes, a new theory addressing the flaws of the Copenhagen quantum mechanics interpretation.

“The Schrödinger equation delineates how a quantum system’s wave function will change through time, an evolution that it predicts will be smooth and deterministic (that is, with no randomness). But that elegant mathematics seems to contradict what happens when humans observe a quantum system, such as an electron, with a scientific instrument (which itself may be regarded as a quantum-mechanical system). For at the moment of measurement, the wave function describing the superposition of alternatives appears to collapse into one member of the superposition, thereby interrupting the smooth evolution of the wave function and introducing discontinuity...

"Many of the founders of quantum mechanics, notably Bohr, Werner Heisenberg and John von Neumann, agreed on an interpretation of quantum mechanics—known as the Copenhagen interpretation— to deal with the measurement problem. This model of reality postulates that the mechanics of the quantum world reduce to, and only find meaning in terms of, classically observable phenomena—not the reverse… Entire generations of physicists were taught that the equations of quantum mechanics work only in one part of reality, the microscopic, while ceasing to be relevant in another, the macroscopic…

"In stark contrast, Everett addressed the measurement problem by merging the microscopic and macroscopic worlds. He made the observer an integral part of the system observed, introducing a universal wave function that links observers and objects as parts of a single quantum system. He described the macroscopic world quantum mechanically and thought of large objects as existing in quantum superpositions as well. Breaking with Bohr and Heisenberg, he dispensed with the need for the discontinuity of a wave-function collapse...

"Everett was not the first physicist to criticize the Copenhagen collapse postulate as inadequate. But he broke new ground by deriving a mathematically consistent theory of a universal wave function from the equations of quantum mechanics itself. The existence of multiple universes emerged as a consequence of his theory, not a predicate” (*Scientific American*).

“Hugh Everett's relative-state formulation of quantum mechanics is an attempt to solve the quantum measurement problem by dropping the collapse dynamics from the standard von Neumann-Dirac formulation of quantum mechanics. Everett then wanted to recapture the predictions of the standard collapse theory by explaining why observers nevertheless get determinate measurement records that satisfy the standard quantum statistics” (*Stanford Encyclopedia*).

Everett’s theory has garnered much support from the scientific community recently and is credited as the source of inspiration for the modern field of quantum computing. He is described by David Deutsch as being “before his time. [Everett] represents the refusal to relinquish objective explanation. A great deal of harm was done to progress in both physics and philosophy by the abdication of the original purpose of those fields: to explain the world. We got irretrievably bogged down in formalisms, and things were regarded as progress which are not explanatory, and the vacuum was filled by mysticism and religion and every kind of rubbish...” (David Deutsch).

IN: Reviews of Modern Physics, Volume 29, Number 3 (July, 1957), pp 454-464. Lancaster, PA and New York, NY: American Institute of Physics. Quarto, original wrappers; custom silk box. A FINE COPY.

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