Content deleted Content added
Johnjbarton (talk | contribs) →Physical approaches to collapse: replace doubled word |
Johnjbarton (talk | contribs) →History: Zeh/Zurek decoherence program. +refs |
||
Line 88:
# The [[probability|probabilistic]], non-[[unitary transformation|unitary]], [[local realism|non-local]], discontinuous change brought about by observation and [[quantum measurement|measurement]] (state reduction or collapse).
# The [[deterministic]], unitary, continuous [[time evolution]] of an isolated system that obeys the [[Schrödinger equation]] (or a relativistic equivalent, i.e. the [[Dirac equation]]).
In 1957 [[Hugh Everett III]] proposed a model of quantum mechanics that dropped von Neumann's first postulate. Everett observed that the measurement apparatus was also a quantum system and its quantum interaction with the system under observation should determine the results. He proposed that the discontinuous change is instead a splitting of a wave function representing the universe.<ref name=SchlosshauerReview/>{{rp|1288}} While Everett's approach rekindle interest in foundational quantum mechanics, it left core issues unresolved. Two key issues relate to origin of the observed classical results: what causes quantum systems to appear classical and to resolve with the observed probabilities of the [[Born rule]].<ref name=SchlosshauerReview/>{{rp|1290}}<ref name=HartleQMCosmology/>{{rp|5}}
Beginning in 1970 [[H. Dieter Zeh]] sought a detailed [[quantum decoherence]] model for the discontinuous change without postulating collapse. Further work by [[Wojciech H. Zurek]] in 1980 lead eventually to a large number of papers on many aspects of the concept.<ref>{{Cite journal |last=Camilleri |first=Kristian |date=2009-12-01 |title=A history of entanglement: Decoherence and the interpretation problem |url=https://www.sciencedirect.com/science/article/pii/S1355219809000562 |journal=Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics |series=On The History Of The Quantum |volume=40 |issue=4 |pages=290–302 |doi=10.1016/j.shpsb.2009.09.003 |issn=1355-2198}}</ref> Decoherence assumes that every quantum system interacts quantum mechanically with its environment and such interaction is not separable from the system, a concept called an "open system".<ref name=SchlosshauerReview/>{{rp|1273}} Decoherence has been shown to work very quickly and within a minimal environment, but as yet it has not succeeded in a providing a detailed model replacing the collapse postulate of orthodox quantum mechanics.<ref name=SchlosshauerReview/>{{rp|1302}}
By explicitly dealing with the interaction of object and measuring instrument, von Neumann<ref name="Grundlagen"/> described a quantum mechanical measurement scheme consistent with wave function collapse. However, he did not prove the ''necessity'' of such a collapse. Although von Neumann's projection postulate is often presented as a normative description of quantum measurement, it was conceived by taking into account experimental evidence available during the 1930s (in particular [[Compton scattering]] was paradigmatic). Later work discussed so-called measurements of the second kind.<ref>
| |||