Interpreting Quantum Mechanics

A Realistic View in Schrodinger's Vein

Lars-Göran Johansson

• Publisher: Routledge
• Year: 2016
• eBook ISBN: 9781351926416
• Topic: Philosophy
• Subtopic: Philosophy History & Theory

Presenting a realistic interpretation of quantum mechanics and, in particular, a realistic view of quantum waves, this book defends, with one exception, Schrodinger's views on quantum mechanics. Johansson goes on to defend the view that the collapse of a wave function during a measurement is a real physical collapse of a wave and argues that the collapse is a consequence of quantisation of interaction. Lastly Johansson argues for a revised principle of individuation in the quantum domain and that this principle enables a sort of explanation of non-local phenomena.

Chapter 1
Interpretative Problems in Quantum Mechanics

1.1 Historical background

The interpretation of quantum mechanics has been a source of conflict ever since its emergence in the 1920s. Schrödinger, de Broglie and Einstein were all of a realistic inclination, whereas Bohr, Heisenberg and several others claimed that the then new theory could not be viewed as a 'literal' description of nature. As the debate continued, the view held by Bohr and Heisenberg, the Copenhagen interpretation, became established among physicists and philosophers. However, the issue has never been finally settled and opponents have repeatedly voiced their doubts. During the last 20 years, the majority view, i.e. the Copenhagen interpretation, has lost ground to alternative interpretations.

One weak point in the Copenhagen interpretation – among many strong ones – is Bohr's claim that we must use classical concepts in order to communicate unambiguously the results of experiments because concepts from microphysics have no clear significance. This sharp distinction between the macro and the micro world however seems completely untenable. Furthermore, the Copenhagen interpretation covers a number of views amounting to a kind of idealism, which cannot be ascribed to Bohr. There are reasons to be hostile to such views.

However, none of the most well-known alternatives, i.e. the many-worlds interpretation and the pilot-wave interpretation, is convincing; on the contrary, these two alternatives seem to be as defective as the Copenhagen interpretation. Some new proposals for interpretation, such as the GRW theory, the modal interpretations of van Fraassen and Dieks' and Healey's interactive interpretation all of seem to have flaws. The GRW theory has internal problems, as is clearly shown by David Albert (1992). Additionally, the central assumption in this theory, namely that there is a fundamental and irreducible probability of collapse proportional to particle number, seems rather ad hoc. The modal interpretations and the interactive interpretation both lack sufficient explanatory force.

The purpose of this treatise is to propose yet another interpretation, or rather reintroduce an old one, based on the idea that quantum mechanics is about real waves, an idea put forward by Schrödinger in the 1920s. However, Schrödinger met severe criticism from, among others, Heisenberg, Planck and Lorentz, and it was generally thought that Schrödinger was wrong. He himself also appeared to come to think so for he did not continue the discussion. However, he was not finally convinced by Bohr and Heisenberg – as can be seen from the recently published proceedings of the Dublin seminars, held at the beginning of the 1950s, where he reiterated and developed his views from the 1920s (Schrödinger, 1995).

There are two likely reasons why Schrödinger did not succeed in convincing his colleagues about the correctness of his wave interpretation: he held a completely classical conception of what a wave is and he did not think that interaction was a process fundamentally quantised. He believed that quantum mechanics one day would be replaced by a better theory in which one could derive quantisation as an effect of resonance between two waves. He is reported to have exclaimed that 'If one has to go on with these damned quantum jumps, then I'm sorry that I ever started to work on atomic theory' (quoted in Rosenthal, 1967, p. 103). As we shall see in Chapter 9, his reliance on a classical wave theory led him into insurmountable difficulties.

The main difference between Schrödinger's view and the one proposed here is the proposition that quantisation is a fundamental principle rather than something that can be derived within a classical wave theory. The similarity is the belief that objects in the micro world are waves, not particles. Stated in one single sentence: quantum mechanics describes a world of waves, which exchange energy discontinuously, and as quantum mechanics so far has proven true in all tests, it is very reasonable to say that that's the way the world is.

1.2 What is an interpretation of a theory?

What do we want when we ask for an interpretation of mechanics? What are the criteria to be met by a successful interpretation?

A moment's reflection over the history of physics tells us that quantum mechanics is alone in triggering such penetrating discussions about interpretation. The reason why we require an interpretation of quantum mechanics whereas we do not. or at least do not to the same extent, when confronted with, for example, relativity theory or classical electromagnetism, is that quantum mechanics, to a high degree, looks like pure mathematics; it is hard to see what kind of things the mathematical entities describe. Quantum mechanics 'makes contact' with nature at certain points only, i.e. the expectation values of observables, but these are few and the rest seems rather a lot of quite formal jiggling with formulas. Compare for example the description of the orbit for a planet around the earth on one hand, and the wave function describing the state of the 2p electron in a hydrogen-like atom on the other. The position of an single orbiting planet could be described in a coordinate system with the sun at the origin by (x(t). y(t)). where x and y fulfil the relation

and the interpretation of this constitutes no problem: starting with an initial position (x₀,y₀ ) and velocity (ẋ(0), ẏ(0)) at the time t₀ = 0 the planet is to be found in the point (x(t), y(t)) for any chosen time t. The functions (x(t), y(t)) and (ẋ(t),ẏ(t)) describe the position and velocity, respectively for the planet at any chosen time t. In compar...

Table of contents

• Cover
• Dedication
• Title
• Copyright
• Contents
• List of Figures and Tables
• Preface
• 1 Interpretative Problems in Quantum Mechanics
• 2 Realism and Understanding
• 3 Individuation and Identity in the Quantum World
• 4 Quantum Objects are Waves
• 5 Particle Behaviour of Waves
• 6 The Measurement Problem
• 7 Quantum Mechanical Spin
• 8 Non-locality
• 9 Gentle Criticism
• 10 Summary and Conclusions
• Bibliography
• Index