I have been interested in quantum mechanics or, synonymously, quantum physics since the very days when I first learned about them as a student. The initial impression was that of an immense mathematical beauty of the formalism of quantum mechanics. The second impression was the fantastic agreement of the theoretical predictions of quantum physics for experiments, and the third and somewhat surprising impression was that there was widespread disagreement about the interpretation of the new theory.
I have been interested in quantum mechanics or, synonymously, quantum physics since the very days when I first learned about them as a student. The initial impression was that of an immense mathematical beauty of the formalism of quantum mechanics. The second impression was the fantastic agreement of the theoretical predictions of quantum physics for experiments, and the third and somewhat surprising impression was that there was widespread disagreement about the interpretation of the new theory.
The difficulties of the old quantum theory were largely dispelled by the development of quantum mechanics in the 1920s. First Heisenberg (1925) developed the rather abstract matrix mechanics and soon after Schro¨dinger (1926; see also Eckart, 1926) developed the physically more appealing wave mechanics. Subsequently he showed them to be mathematically equivalent. The physicists were greatly relieved; now they had once again a mathematical formalism that enabled the results of experiments to be calculated. It was possible to move forward. It is certainly a very elegant and indeed beautiful formalism, and does enable the results of many physical measurements to be calculated with great accuracy. It is used daily by atomic and nuclear physicists; there is no other way to make calculations. From the earliest days there has been intense debate about the interpretation of quantum mechanics, and it shows no signs of being settled; if anything it is becoming more intense over the years. As Penrose has remarked, no one understands quantum mechanics. Feynman (1967; see also Sykes, 1994) also admitted that ‘nobody understands quantum mechanics’, and Einstein once remarked: ‘I have thought a hundred times as much about the quantum problems as I have about general relativity theory’ (Pais, 1994, p. 57). It should therefore be evident that the most that can be done here is to try to show where the real difficulties lie, and how the failure to recognize that quantum mechanics is an essentially statistical theory has led to a series of confusing quantum paradoxes. It is just these paradoxes that have often been used to support theological speculations. It is useful to ask what ‘understanding quantum mechanics’ actually means. Certainly it means being able to calculate the results of many measurements. The same applies to Newton’s theory of gravitation, which we understand in the sense that we can use it as a basis of calculation, although we do not really understand the gravitational force itself. Very often, especially in modern physics, the mathematical formalism does not give us the sort of intuitive physical feeling for what is going on that we often obtain from classical mechanics. Perhaps we can never achieve more than this for quantum mechanics. In classical mechanics we can assume that a property that is measured objectively exists prior to the interaction of the measuring apparatus with the observed system. Quantum mechanics, however, ‘is incompatible with the proposition that measurement discovers some unknown but pre-existing property’ (Peres, 1997, p. 14). There is an important distinction between mysteries and absurdities. We may be forced to live with mysteries, but there is no reason why we should put up with absurdities such as the wave-particle duality, tunnelling through potential barriers, acausal events and the collapse of the wave function. These are the quantum paradoxes that will be discussed later on. They arise within the Copenhagen interpretation of quantum mechanics and are solved by other interpretations. These alternative interpretations enable us to make conjectures about what is going on, even though we cannot understand it in detail. This is acceptable and a stimulus to further research. It is certainly difficult enough to understand quantum mechanics, but there is no need to try to visualize logical absurdities in the effort to do so. Quantum mechanics is a mathematical formalism that makes it possible to calculate the results of some experiments. Anything more than this, such as questions about the interpretation of what is measured and whether it tells us what is actually going on in the system being studied, belongs to philosophy. Thus we are concerned here with what is essentially a philosophical debate; if it were just a matter of physics the debate would have been settled long ago. One of the difficulties is that it invokes the results of experiments and uses the language of quantum mechanics. Inevitably this language uses philosophical terms and then it is easy to give the impression that the philosophical propositions are in some way entailed by the physical results. These in turn can influence theological thinking. In order to be quite clear which arguments are justified and which are not, it is essential to separate the three levels of discourse: physical, philosophical and theological. Our task is to relate these together, and this immediately raises the traditional problems of the philosophy of science, including the relation of experiment to theory, and of theory to explanation. We begin by discussing experiments, distinguishing between those that are real and those that are imaginary.
Recent years have seen increased interest towards quantum physics education research, and the topic has been studied from many perspectives both empirically and theoretically. The consensus of previous studies has been that the theory poses an exceptional challenge for learning and teaching, warranting more attention and further research. This dissertation aims to contribute to this discussion by asking what the underlying reasons for these challenges are and how they could potentially be alleviated. On one hand, the topic is approached from an interpretational point of view, considering the ontological foundations of the theory. It is argued that many of the fundamental difficulties in learning and teaching quantum mechanics stem from the ontological foundations of the theory. On the other hand, the historical development and the mathematical structure of the theory are discussed from an educational point of view. The dissertation consists of five articles that explore the above themes from different perspectives. The first study considers the development of one historical formulation of quantum mechanics, namely matrix mechanics. In general, the historical development of quantum theory has been complex and meandering, and its results may seem confusing to students. In our study, we discuss the use of matrix mechanics in quantum mechanics instruction to provide students with a clearer picture of the theory, its historical development, and the relations between its various formulations and used formalisms. The second and third studies add to the discussion on the roles of mathematics in physics and physics education. In quantum mechanics, the role of mathematics is especially pronounced, as the understanding of the theory heavily relies on its mathematical framework. Therefore, we argue that the focus of quantum mechanics instruction should be shifted away from calculational aspects to a more integrated approach that treats the conceptual and mathematical sides of the theory intertwined. In our studies, we provide an overview of the roles assigned to mathematics in previous physics education research literature and present our own layered characterisation of the roles, aiming at diversifying the discussion on the roles of mathematics within the physics education research community and in physics instruction. The fourth and fifth studies empirically examine the challenges of quantum mechanics instruction in the context of an introductory quantum mechanics course. In the fourth study, we explore the effect of initial mathematics knowledge and self-efficacy on student learning, while in the fifth study, we consider the effects of the instructional approach and different teaching strategies on student conceptual knowledge and self-efficacy. The specific focus is on the impact of implementing a new instructional approach, the so-called spin first approach, that emphasises the mathematical basis and conceptual understanding of the theory instead of repeated mathematical calculations. Our results show that the spin-first approach, combined with an active learning model, is able to foster a high level of student self-efficacy and conceptual learning. Quantum mechanics is one of the most successful theories in the history of physics. Nevertheless, learning and teaching its basic principles continue to pose significant challenges for both instructors and students. In this dissertation, we argue for an approach to teaching the theory that places greater emphasis on its mathematical foundations and treats physics and mathematics as intertwined disciplines.
When investigating various interpretations of quantum mechanics one notices that each interpretation contains an element which escapes a complete and full description. This element is always associated with the stochasticity of the individual event in the quantum measurement process. It appears that the implications of this limit to any description of the world has not been sufficiently appreciated with notable exceptions of, for example, Heisenberg, Pauli and Wheeler. If we assume that a deeper foundation of quantum mechanics is possible, the question arises which features such a philosophical foundation might have. It is suggested that the objective randomness of the individual quantum event is a necessity of a description of the world in view of the significant influence the observer in quantum mechanics has. It is also suggested that the austerity of the Copenhagen interpretation should serve as a guiding principle in a search for deeper understanding. In recent years, a significant increase of interest in the foundations of quantum mechanics can be observed. This increase is certainly related to the immense progress made during the last two decades in experiments with individual quantum systems. This technological progress has made it possible to really perform more and more of the famous gedanken experiments which were so important in the early days of the theory. Not only did these experiments confirm the theory in every detail, they also opened up avenues for new experimental directions which might even lead some day to new technology. While such applications are certainly still far away, areas like quantum cryptography[1], quantum computation[2] and interaction-free measurement[3], just to name a few examples, certainly deserve the attention they receive. All this activity has also drawn more attention to the problems of understanding and interpreting quantum mechanics. It seems that there, a definitive consensus has not yet been reached. As witnesses quote authorities like Feynman as saying[4]: I think can safely say that nobody today understands quantum mechanics, whereby he apparently included himself, or like Roger Penrose[5], who describes his opinion remarking that while the theory agrees incredibly well with experiment and while it is of profound mathematical beauty, it makes absolutely no sense. Why did even physicists who have contributed so significantly to quantum theory Feynman was even rewarded the Nobel Prize for one of its mathematical formulations choose such emphatic and strong formulations? Why is it that the average physicist hears very little about such problems during his/her education? Why is the comprehension of the theory very often focused on formalism while questions that probe for deeper meaning are usually not tackled? To take a closer look at the situation, let us turn to a brief analysis of the interpretation of quantum mechanics. We note that there are at least two levels of interpreting a formalism, a physical theory. The first, basic, level supplies the rules that determine which element of the formalism corresponds to which measurable quantity or to which observable fact in a concrete experimental situation. Theses rules are a large, mostly not explicated but only implicit, set of instructions. These instructions concern the manner of working with the statements of the theory in order to obtain predictions for future experiments or events, and they concern the instructions on how to proceed in experiment in order to demonstrate or test a theoretical
Abstract It can easily be argued that a fully mature and complete knowledge of quantum mechanics should include historical, axiomatic, formal mathematical, and even philosophical background to the subject. However, for a student approaching quantum theory for the first time in a serious way, it can be the case that an approach utilizing his or her existing knowledge of, and intuition for, classical physics (including mechanics, wave physics, and electricity and magnetism) as well as emphasizing connections to experimental results can be the most pro- ductive. That, at least, is the point of view adopted in this text and can be illustrated by a focus on the following general topics: