This paper explores how experiments influence the reception of interpretations of quantum mechanics, and also other relations between experiments and interpretations in that field. We start by surveying the struggle of different schools of philosophy of science in the 19th and early 20th centuries to adapt to the scientific advances, and then give a brief overview of realist and antirealist interpretations in quantum mechanics. Eight different types of relations between interpretations and experiments are then examined, with case studies from the history of quantum mechanics. (1) Many interpretations agree with all of the predictions of the instrumentalist interpretation, which is a good strategy for survival. (2) Some interpretations make different predictions that are not testable. (3) Other interpretations constitute ‘a different theory’ and are testable, although sometimes this is not anticipated by the interpretation. (4) Some interpretations have generated many variations, by adjustment of parameters or hypotheses, and part of these variations have been tested and ruled out by experiment. (5) At times experiments reinforce an interpretation. (6) Some experiments lead to a refinement of the interpretation. (7) There are experiments that suggest the creation of an interpretation. (8) And there are cases in which experiments are suggested by an interpretation, while not affecting its rivals.
This paper explores how experiments influence the reception of interpretations of quantum mechanics, and also other relations between experiments and interpretations in that field. We start by surveying the struggle of different schools of philosophy of science in the 19th and early 20th centuries to adapt to the scientific advances, and then give a brief overview of realist and antirealist interpretations in quantum mechanics. Eight different types of relations between interpretations and experiments are then examined, with case studies from the history of quantum mechanics. (1) Many interpretations agree with all of the predictions of the instrumentalist interpretation, which is a good strategy for survival. (2) Some interpretations make different predictions that are not testable. (3) Other interpretations constitute ‘a different theory’ and are testable, although sometimes this is not anticipated by the interpretation. (4) Some interpretations have generated many variations, by adjustment of parameters or hypotheses, and part of these variations have been tested and ruled out by experiment. (5) At times experiments reinforce an interpretation. (6) Some experiments lead to a refinement of the interpretation. (7) There are experiments that suggest the creation of an interpretation. (8) And there are cases in which experiments are suggested by an interpretation, while not affecting its rivals.
Quantum mechanics has continually challenged our understanding of reality. Throughoutits history, pivotal experiments have forced physicists to reconsider and refine how we inter-pret the theory’s mathematical formalism. This review surveys a series of landmark quantumexperiments from the early 20th century to the present day, examining how each experimentaltered the landscape of quantum interpretations. Beginning with the foundational phenomenathat necessitated the quantum hypothesis, we move through classic tests of wave-particle du-ality and the role of observation. We then explore the profound implications of entanglementvia Einstein-Podolsky-Rosen correlations and Bell’s theorem, along with the experiments thatultimately confirmed quantum nonlocality. Further, we discuss delayed-choice and quantumeraser experiments that probe the interplay of measurement and reality, multi-particle interfer-ence tests that go beyond Bell’s inequalities, and increasingly ambitious e!orts to push quantumphenomena to macroscopic scales. By analyzing these experiments and the theoretical debatessurrounding them, we illustrate how experimental evidence has driven the evolution of inter-pretations of quantum mechanics. In doing so, we highlight the ongoing dialogue betweenexperimental insight and philosophical interpretation in quantum physics.
Abstract This chapter surveys various proposals to interpret—that is, make sense of—quantum mechanics. We could attempt to think of quantum mechanics in purely instrumentalist terms, as an algorithm to predict observed experimental results. But this fits badly with scientific practice and is probably not viable. We could attempt to modify quantum mechanics itself to resolve the paradoxes, and there are some simple models that attempt to do that: some are ‘hidden-variable’ theories that add extra properties to the theory, some are ‘dynamical-collapse’ theories that modify the theory’s equations. But none of these models succeed in reproducing quantum theory’s predictions outside a relatively narrow range of applications. Or we could try to take the apparent indefiniteness of quantum mechanics literally, and interpret it as a theory of many parallel worlds. The correct interpretation of quantum mechanics remains controversial, but the search for understanding and interpretation of the theory has led to very substantial scientific results and is likely to lead to more.
The article examines the controversial relation of scientific realism with quantum mechanics. To this end, two distinct discussions are invoked: the discussion about ‘realism’ in the context of quantum mechanics and the discussion about ‘scientific realism’ in the context of the general philosophy of science. The aim is to distinguish them in order, first, to argue that the former—revolving around ‘local realism’ and the theorems of Bell and Kochen–Specker—unjustifiably identifies realism with features of a particular worldview, and thereby fosters the impression that the failure of ‘local realism’ in quantum experiments constitutes a failure of scientific realism too; and, second, in light of the latter discussion, to claim that scientific realism and quantum mechanics can be compatible—there is ground for dealing with quantum measurement simply as a physical mind-independent interaction. Therefore, a realist approach to the theory is possible despite its notorious measurement problem, even if the issue of its interpretation is still disputed.
My aim in this dissertation is to defend a realist interpretation of quantum mechanics.Firstly, I present considerations based on certain general features of theories in the natural sciences which indicate that realism affords a better account of those theories than instrumentalism.In particular, I consider certain issues surrounding the cognitive status of theories, including the role of models, the status of scientific explanation, and the referential character of theoretical terms.Secondly, I develop a detailed realist theory of measurement based on the notion of quantity terms as designators of objective properties of, and relations among, existing entities.I contrast this with the leading instrumentalist theories of measurement, and I argue that the realist theory is the better account of both the logic and practice of scientific measurement.Finally, I consider a number of objections to realism that arise because of certain theoretical features peculiar to quantum mechanics.In the course of this discussion, I consider crucial experimental evidence for the "dual" nature of microentities, various criteria of reality proposed by philosophers of science, the peculiar features of quantum mechanical measurement, and the status of causality in quantum mechanics.I argue that while certain realist viii ix interpretations of the quantum theory, namely the wave and wavicle interpretations, are unsatisfactory, an interpreta tion which construes micro-entities as existing particles is a tenable account.CHAPTER I ignored the considerations which arise at those more general levels of inquiry, but one can not adequately assess the status of quantum mechanics with respect to both realism and instrumentalism apart from those considerations.In the second two chapters of the dissertation, I shall argue that realist interpretations of quantitative theories in the natural sciences are preferable to instrumentalist interpretations.Then in the remainder of the dissertation, I shall go on to argue that realism is tenable at the quantum mechanical level despite the features peculiar to that theory.CHAPTER II THE COGNITIVE STATUS OF THEORIES transitions from one set of experiential statements to another.This view is in marked contrast to that of the realist who regards such terms as referential.This divergence in opinion between realists and instrumentalists about the referential character of theoretical terms leads to a related dispute over the role of models in the inter pretation of scientific theories.Before contrasting the various philosophical positions on this issue, it will be necessary to sort out different senses of the term "model."Upon inspecting the literature surrounding this dispute, it seems that much of the controversy about the role of models stems from a failure to make such distinctions.I will begin this task by distinguishing between 13 model-structures and model-objects.A model-structure is a definitely specifiable schema of mathematical-logical relationships which is exhibited by and can be abstracted from a set of objects.Any set of objects which exhibits a model-structure constitutes a set of model-objects.With respect to any particular scientific theory, there may be a variety of model-objects that scientists employ for various purposes.For example, in the kinetic theory of gases, one can distinguish the following.Firstly, there is the set of molecules themselves, the theoretical entities which we shall 13.For further detail in this regard, see Henry C. Byerly, "Model-Structures and Model-Objects," British Journal for the Philosophy of Science.Vol. 20, 1969, pp.135-144.i In fact, if one were to make that claim, I do not see how it could be supported without again falling prey to Maxwell's criticism cited above.And if one is simply troubled by the "ontological risk" involved in asserting the existence of theoretical entities because of the tentativeness of the corresponding theories, it should be noted that the risk of being wrong is a small price to pay for the potentially deeper understanding of nature that scientific theories afford us in the light of realist commitments.
Quantum mechanics approaches its centenary with an impressive record. It became the backbone of most research in physics, led to applications such as the transistor and laser, and prompted an upheaval in the philosophy of science. Its scope and its precision have been constantly growing, and it is now promising more powerful computers and safer cryptography. This century of conquests has also been a time of ongoing debates about the foundations and interpretation of the theory, which has been referred to as the quantum controversy. The controversy has been unusually long and remains open. Jammer called it “a story without an ending” and Laloë described this coexistence of successes and doubts with the metaphor of the colossus with feet of clay. This Handbook is a survey on this history. Some of the so-called “interpretations” are not interpretations of a fixed formalism, they are different theories, thus it has been a debate about the interpretations and the foundations of quantum mechanics. In this volume, the “history of interpretations” is used for the sake of brevity. The successive parts of the Handbook deal with the scientific and philosophical issues under debate, historical landmarks, places and contexts, historical and philosophical theses, and the proliferation of interpretations. This Handbook may serve those interested in the history of quantum mechanics and those who are engaged with, or attracted by current research on quantum information, as it may give them a flavor of the history that led to or lay the groundwork for the current investigations.
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