“It has always seemed to me that the hard thing to understand is not quantum mechanics, but where classical mechanics comes from (in the sense of how it emerges from a “measurement”).”

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Peter Woit4

American physicist 1957

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“Certainly we do not need quantum mechanics for macroscopic objects, which are well described by classical physics – this is the reason why quantum mechanics seems so foreign to our everyday existence.”

Alain Aspect (1947) French physicist

"Introduction: John Bell and the second quantum revolution" (2004)

“People get a lot of confusion, because they keep trying to think of quantum mechanics as classical mechanics”

Sidney Coleman (1937–2007) American physicist

Quantum Mechanics in Your Face http://www.physics.harvard.edu/about/video.html, a lecture given by Sidney Coleman at the New England sectional meeting of the American Physical Society (Apr. 9, 1994)

“Considering the pervasive importance of quantum mechanics in modern physics, it is odd how rarely one hears of efforts to test quantum mechanics experimentally with high precision.…The trouble is that it is very difficult to find any logically consistent generalization of quantum mechanics. One obvious target for generalization is the linearity of quantum mechanics, but if we arbitrarily add nonlinear terms to the Schrodinger equation, how do we know that the theory we obtain will have a sensible physical interpretation? At least in part, it is the dearth of generalized versions of quantum mechanics that has made it so hard to plan experimental tests of quantum mechanics.”

Steven Weinberg (1933) American theoretical physicist

"Testing Quantum Mechanics" http://www.sciencedirect.com/science/article/pii/0003491689902765, Annals of Physics (1989)

“It seems to me that we must make a distinction between what is "objective" and what is "measurable" in discussing the question of physical reality, according to quantum mechanics.”

Roger Penrose book The Emperor's New Mind

Source: The Emperor's New Mind (1989), Ch. 6, Quantum Magic and Quantum Mastery, p. 269.
Context: It seems to me that we must make a distinction between what is "objective" and what is "measurable" in discussing the question of physical reality, according to quantum mechanics. The state-vector of a system is, indeed, not measurable, in the sense that one cannot ascertain, by experiments performed on the system, precisely (up to proportionality) what the state is; but the state-vector does seem to be (again up to proportionality) a completely objective property of the system, being completely characterized by the results it must give to experiments that one might perform.

“Weinberg says that "we want to know what's happening out there". But this is just the standard anti-quantum zealots' misunderstanding of the essence of quantum mechanics. Quantum mechanics says that all knowable things about the physical system must be obtained through a measurement whose outcomes are predicted via the Born rule. There is nothing else happening out there, at least nothing else knowable that is happening out there! So quantum mechanics does answer the question what is happening out there and the claim that quantum mechanics is incomplete in this sense is simply a lie.”

Luboš Motl (1973) Czech physicist and translator

https://motls.blogspot.com/2018/09/a-recent-dissatisfied-weinbergs-talk-on.html <br class="br"> The Reference Frame http://motls.blogspot.com/

“To know the quantum mechanical state of a system implies, in general, only statistical restrictions on the results of measurements. It seems interesting to ask if this statistical element be thought of as arising, as in classical statistical mechanics, because the states in question are averages over better defined states for which individually the results would be quite determined. These hypothetical 'dispersion free' states would be specified not only by the quantum mechanical state vector but also by additional 'hidden variables' - 'hidden' because if states with prescribed values of these variables could actually be prepared, quantum mechanics would be observably inadequate.”

John S. Bell (1928–1990) Northern Irish physicist

On the problem of hidden variables in quantum mechanics (1966)

“I would not call [entanglement] one but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought.”

Erwin Schrödinger (1887–1961) Austrian physicist

italics in the original

DISCUSSION OF PROBABILITY RELATIONS BETWEEN SEPARATED SYSTEMS (1935)

“I liked quantum mechanics very much. The subject was hard to understand but easy to apply to a large number of interesting problems.”

Willis Lamb (1913–2008) American Physicist

W. E. Lamb, Super classical quantum mechanics: the best interpretation of non relativistic quantum mechanics, Am. J. Phys. 69, 413-422 (2001).

“The first charge against 'measurement', in the fundamental axioms of quantum mechanics, is that it anchors there the shifty split of the world into 'system' and 'apparatus'. A second charge is that the word comes loaded with meaning from everyday life, meaning which is entirely inappropriate in the quantum context.”

John S. Bell (1928–1990) Northern Irish physicist

Against 'measurement' (1990)

“Quantum mechanics is weird. I don't understand it. Just live with it. You don't have to understand the nature of things in order to build cool devices…If you can figure out how to take advantage of this quantum multitasking, we can build computers that can do computations that no classical computer could do even if it were the size of the entire universe.”

Seth Lloyd (1960) American engineer

Seth Lloyd, cited in: Scott Dewing (2011) "Seth Lloyd on quantum computing" blog.insidethebox.org, 9/23/2011

“It has always seemed to me that the hard thing to understand is not quantum mechanics, but where classical mechanics comes from (in the sense of how it emerges from a “measurement”).”

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Peter Woit4

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