Notes

Gnój - Streszczenie, Problematyka
Rob Clifton and Hans Halvorson (1999, 2002) argue that Bohm’s interpretation of quantum mechanics can be seen as a special case of Bohr’s complementarity interpretation if it is assumed that all measurements ultimately reduce to positions measurement. From these assumptions they conclude that Bohm’s hidden variables are none other than the “value states” that the complementarity interpretation postulates if position measurement were always dynamically significant, but this metaphysical restriction is not, as their results indicate, demanded by the physics. A re-assessment of Bohr’s philosophy of quantum mechanics is made by Whitaker (2004) on the basis of Clifton and Halvorson’s and Dickson’s works and in the light of quantum information theory. Originally Jeffrey Bub and Clifton (1996) were able to demonstrate (given some idealized conditions) that Bohr’s complementarity and Bohm’s mechanics fall under their uniqueness theorem for no-collapse interpretations. By following Zinkernagel, he claims that this problem is somewhat softened by Bohr’s contextualist theory of measurement. Despite this position Dorato argues that in dyplom to justify his entity realism and anti-instrumentalist interpretations, Bohr also needed to postulate something ontologically distinct from the realm of quantum mechanics, a claim that creates the well-known problem of defining in i non-ambiguous and exact way the cut between the classical and the quantum realm.

Hence if one does not argue for spontaneous collapse of the wave function, hidden variables, or many worlds, one needs to supplement quantum mechanics with a classical description of measuring instruments in terms of clocks and rods. This problem arises from the fact that quantum mechanics itself cannot account for why experiments on objects in a state of superposition always produce a definite outcome. Moreover, Bohr believed for epistemic reasons that we had to use classical language because this language is a refinement of our everyday language, which is adapted to describe our sensory experience and therefore the only language that can endow the quantum formalism with an empirical content. The quantum formalism can predict the statistical outcome of these interactions but it cannot say anything about the trajectory of objects. So when Bohr regarded quantum mechanics as a rational generalization of classical physics, he always thought of it as a way to secure the epistemic validity of quantum mechanics and not a way to save a classical ontology. But parallel with the growing awareness of the essential differences between Bohr’s and Heisenberg’s understanding of quantum mechanics several philosophers of science have revitalised Bohr’s view on complementarity. The pragmatic reasons seem to be reasonably clear.

But during a measurement we need to separate the system from the measuring instrument and the environment for pragmatic reasons. Hence, according to Dieks, Bohr assumed that it is only an epistemic necessity to describe “some systems classically in medal to have a pragmatic starting point for the treatment of other systems.” Bohr’s demand of using classical concepts for epistemic reasons has no implications for his view that macroscopic objects are quantum objects. The measurement interaction determines which correlations are forged with the micro-world. Philosophers have also started to explore the idea of decoherence in relation to Bohr’s view about “the inseparability of the behavior of the object and the interaction with the measuring instrument” or “the uncontrollable interaction between the atomic system and measurement apparatus.” (Schlosshauer and Camilleri 2011, 2017; Camilleri and Schlosshauer 2015; Bächtold 2017; and Tanona 2017). Although Bohr assumed that the measuring apparatus is altogether a quantum mechanical system, he nevertheless believed that the instrument could be approximately described by classical theory. Henrik Zinkernagel (2015, 2016) may seem to get close to Bohr’s view when he argues that Bohr not so much solved the measuring problem as he dissolved it. Measuring devices are not classical objects even though we need classical concepts to describe our general physical experiences and the outcome of quantum experiments.

The distinction between classical and quantum (both ontic and epistemic) is contextual. Every system can in principle be treated quantum mechanically, but since we always need a frame of reference to describe experimental outcomes, not all systems can be treated quantum mechanically at once. The implication is that Bohr did not exclude the application of quantum theory to any system. It turns out that either position or momentum are dynamically significant, but it is not permissible to assume that position and momentum are both dynamically significant in any single context. The measuring device itself, if macroscopic and under ordinary circumstances (so that it really is a measuring device that can be used by us) allows both position and momentum talk in its own description. Moreover, he also maintains that Bohr’s discussions of spin, a property much less frame dependent than position and momentum, were very different from his discussions of the latter, and based on these differences he offers a Bohrian account of Bell’s theorem and its significance. This explains both Bohr’s epistemic reliance on the domain of classical physics and his ban of any attempt to construct classical objects from quantum objects. pomoce naukowe He thinks that the measurement problem is ultimately a consequence of ontological quantum fundamentalism (that everything is quantum).


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