The Copenhagen interpretation is an interpretation of the quantum domain that emerged from the pioneering work of Heisenberg, Schrodinger, Born, and De Broglie. On the Copenhagen interpretation the observational level is a portion of the language of ordinary experience, augmented by the classical theories of mechanics and electromagnetism. The Copenhagen interpretation places an additional restriction on theoretical-level interpretations. The calculations of both quantum theory and special relativity theory exhibit asymptotic agreement with the calculations of classical theory. N. R. Hanson maintained that one important feature of the Copenhagen interpretation is Bohr's insistence that all empirically testable statements within quantum theory are ultimately about "phenomena". Pictorial-level interpretations may take the form of mutually exclusive descriptions of a quantum system in terms of classical particles or classical waves. Critics of the Copenhagen interpretation take the failure of the "causal attribution implies explanation" thesis at the pictorial level to be a good reason to eliminate this level of interpretation.
The Copenhagen interpretation is an interpretation of the quantum domain that emerged from the pioneering work of Heisenberg, Schrodinger, Born, and De Broglie. On the Copenhagen interpretation the observational level is a portion of the language of ordinary experience, augmented by the classical theories of mechanics and electromagnetism. The Copenhagen interpretation places an additional restriction on theoretical-level interpretations. The calculations of both quantum theory and special relativity theory exhibit asymptotic agreement with the calculations of classical theory. N. R. Hanson maintained that one important feature of the Copenhagen interpretation is Bohr's insistence that all empirically testable statements within quantum theory are ultimately about "phenomena". Pictorial-level interpretations may take the form of mutually exclusive descriptions of a quantum system in terms of classical particles or classical waves. Critics of the Copenhagen interpretation take the failure of the "causal attribution implies explanation" thesis at the pictorial level to be a good reason to eliminate this level of interpretation.
A brief account of the world view of classical physics is given first. We then recapitulate as to why the Copenhagen interpretation of the quantum mechanics had to renounce most of the attractive features of the clasical world view such as a causal description, locality, scientific realism and introduce a fundamental distinction between system and apparatus. The crucial role is played in this by the Bohr's insistence on the wavefunction providing the most complete description possible for an even individual system. The alternative of introducing extra dynamical variables, called hidden variables, in addition to the wavefunction of the system so as to be able to retain at least some of the desirable features of classical physics, is then explored. The first such successful attempt was that of Bohm in 1952 who showed that a realistic interpretation of the quantum mechanics can be given which maintains a causal description as well as does not treat systems and measuring appeartus differently. We begin with the construction of the Bohm's theory. He introduces particle positions as the hidden variables. The particle positions play a special role in Bohm theory. The particle trajectories are guided by the wavefunction. The Bohm theory is deterministic. The probability enters through a special assumption, ``quantum equilibrium'' hypothesis, for the initial conditions on the ensemble of particle trajectories. The ``wave or particle'' dilemma is resolved by a ``wave and particle'' resolution. The measurements in Bohm theory can be described without mysticism. Bohm's theory is however nonlocal.
This Anti-Copenhagen interpretation [compare with N. R. Hanson, Am. J. Phys. 27, 1 (1959)] submits that the doctrine of an inherent double nature of matter (and of light) is a most uneconomical hypothesis which would never have been proposed (except for heuristic purposes) had it not been for an oversight of the mechanical particle theory of diffraction by Duane (1923), later incorporated into the quantum mechanics of 1926 in Born's unitary statistical interpretation of wavelike phenomena. Bohr's indeterminacy view comes from a verbal translation of a legitimate wave feature; it is contrasted to the uncertainty of prediction of exact results. The latter is supported by the experiment, the former is not, so that various “epistemological lessons” drawn from Bohr's view stand on brittle ground, which can hardly be reinforced by pointing to the transformation from the first to the second quantization, i.e., from one to another form of a complete and unitary theory. The simple quantum rules of the particle theory (first quantization) can be reduced to general postulates of symmetry and invariance.
In the past both instrumentalism and empiricism have inspired certain pragmatic elements into the Copenhagen interpretation of quantum mechanics. The relation of such pragmatisms with the correspondence principle is discussed. It is argued that neither Bohr nor Heisenberg did take `correspondence' in one of these forms, and that it, in particular, was Bohr's classical attitude which caused him to apply in an inconsistent way his correspondence principle to the Einstein-Podolsky-Rosen experiment, thus causing much confusion. It is demonstrated that an empiricist pragmatism is conducive to an explanation of violation of the Bell inequalities as a consequence of `complementarity' in the sense of `mutual disturbance in a joint nonideal measurement of incompatible observables' rather than as being caused by `nonlocal influences'.
The interpretation of quantum mechanics has been controversial since the introduction of quantum theory in the 1920s. Although the Copenhagen interpretation is commonly accepted, its usual formulation suffers from some serious drawbacks. Based mainly on Bohr's concepts, the formulation assumes an independent and essential validity of classical concepts running in parallel with quantum ones, and leaves open the possibility of their ultimate conflict. In this book, Roland Omnes examines a number of recent advances, which, combined, lead to a consistent revision of the Copenhagen interpretation. His aim is to show how this interpretation can fit all present experiments, to weed out unnecessary or questionable assumptions, and to assess the domain of validity where the older statements apply. The text offers a self-contained treatment of interpretation (in nonrelativistic physics) in a manner accessible to both physicists and students. Although some hard results are included, the concepts and mathematical developments are maintained at an undergraduate level. This book enables readers to check every step, apply the techniques to new problems and make sure that no paradox or obscurity
In the past both instrumentalism and empiricism have inspired certain pragmatic elements into the Copenhagen interpretation of quantum mechanics. The relation of such pragmatisms with the correspondence principle is discussed. It is argued that neither Bohr nor Heisenberg did take ‘correspondence’ in one of these forms, and that it, in particular, was Bohr’s classical attitude which caused him to apply in an inconsistent way his correspondence principle to the Einstein-Podolsky-Rosen experiment, thus causing much confusion. It is demonstrated that an empiricist pragmatism is conducive to an explanation of violation of the Bell inequalities as a consequence of ‘complementarity’ in the sense of ‘mutual disturbance in a joint nonideal measurement of incompatible observables’ rather than as being caused by ‘nonlocal influences’.
Of all the many rival interpretations of quantum mechanics, none is more important or influential than the Copenhagen interpretation. Unfortunately, there is no one Copenhagen interpretation of quantum mechanics. If one uses the expression, and everyone does, one should not think of the Copenhagen interpretation as a single consistent interpretation of the theory. Philosophers of physics tend to use the expression ‘the Copenhagen interpretation of quantum mechanics’ as a label covering a variety of different interpretations all of which either originate with Niels Bohr or were invented by him, his colleagues and guests at the Institute for Theoretical Physics in Copenhagen beginning in the middle 1920s. Perhaps one should say that the Copenhagen interpretation in this diffuse sense goes back farther than this, back even before the rise of the new quantum mechanics. Heisenberg tells the story of a boat trip he, Bohr, and some friends took from Copenhagen to the island of Fyn around the time when the then new quantum mechanics was being developed. Bohr, ‘full of the new interpretation of quantum theory’, talked of ‘the difficulties of language, of the limitations of all our means of expressing ourselves’ and of how these limitations had been expressed ‘in the foundation of atomic theory in a mathematically lucid way’. ‘Finally,’ Heisenberg ends the story, ‘one of the friends remarked drily, “But, Niels, this is not really new, you said exactly the same ten years ago”