If Physics Is an Information Science, What Is an Observer?

Relational Quantum Mechanics (RQM) claims to be an interpretation of quantum theory \cite{Rovelli.21}. However, there are significant departures from quantum theory: (i) in RQM measurement outcomes arise from interactions which entangle a system S and an observer A without decoherence, and (ii) such an outcome is a "fact" relative to the observer A, but it is not a fact relative to another observer B who has not interacted with S or A during the foregoing measurement process. For B the system S⊗A remains entangled. We derive a GHZ-like contradiction showing that relative facts described by these statements are incompatible with quantum theory. Hence Relational Quantum Mechanics should not be considered an interpretation of quantum theory, according to a criterion for interpretations that we have introduced. The criterion states that whenever an interpretation introduces a notion of outcomes, these outcomes, whatever they are, must follow the probability distribution specified by the Born rule.

I argue that philosophical reflection can contribute to a better understanding of physical theories by performing conceptual clarification, epistemological analysis and ontological exploration. I begin by reconstructing early ontological interpretations of quantum theory, i.e., by explaining Copenhagen instrumentalism and the shift toward a quantum realism. I turn to entanglement, whose chief philosophical challenge is to understand which deeper property of nature it reveals. The trouble is that the EPR-correlations it gives rise to are not produced by common causation. Conceptual analysis shows that this failure is due to the violation of separability in quantum theory. In entangled states, it is the composite state that is primary since it cannot be neatly divided into two states that unambiguously pertain to the partial systems. As a result, total states are not produced by an interaction among the parts. This feature can be interpreted in ontological terms as suggesting a holist picture of nature. Another question of philosophical import concerns the quantum measurement problem and the contribution decoherence makes to its solution. The conceptual point is what, precisely, this problem amounts to and what we require considering it settled. The issue that divides the philosophical factions is whether a solution needs to show that superpositions are actually destroyed or whether it suffices to demonstrate that superpositions become unobservable.

For more than eighty years, quantum theory (QT) has dominated physical science. This domination remains unchallenged to this day. Some physicists celebrate this remarkable stability. Others lament this fact and argue that QT inhibits our understanding of physical reality. They feel that numerous problems that have accumulated in physical science require stepping beyond the horizon outlined by QT. The article offers a critical examination of the foundational assumptions of QT that shape its practice. It uses two interpretations of QT as case studies—Copenhagen interpretation and the theoretical perspective advanced by American physicist David Bohm—to explain one major problem that continues to plague our study of physics. The article sketches a path to a possible solution and outlines a new science practice that this solution will require.

The STA is a mathematical system, rather than of itself containing new physics. However, when we employ it in the description of physical phenomena, we usually find that some fresh insight is obtained, often on old questions. The oldest question of 20th century physics is the interpretation of quantum mechanics, and in this lecture we aim to discuss some of the light that an STA approach can throw upon this issue. This will be undertaken in the context of specific examples, and so in the main these lecture notes contain the details of these, rather than the comments that will be made about issues of interpretation. We think these examples stand as interesting and important applications in their own right, irrespective of whether one thinks there is a problem to be solved in the interpretation of quantum theory. This is particularly true for the beginnings of a multiparticle STA approach which we describe here, since it seems undeniable that there is a need for a more coherent and justifiable rationale for the set of recipes and operational procedures that currently constitute relativistic multiparticle theory.KeywordsQuantum TheoryDirac EquationGeometric AlgebraSpin VectorPauli PrincipleThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

This article1 presents a two-part proposal aimed at exploring “reality” through unifying perspectives and universally consistent foundations. Both parts are inspired by Erwin Schrödinger’s principle of objectivation, particularly the function of the ‘Subject of Cognizance’ embedded within it, and the (seemingly unresolvable, yet inescapable!) issue of the ‘location’ of the boundary between the ‘observed’ and the ‘observer’ that arises in the interpretation of quantum theory. In the first part, it is argued that different interpretations of quantum theory could be viewed as complementary rather than as alternatives, for each interpretation provides insight into different aspects of reality, and thus, integrating perspectives from multiple quantum interpretations can offer a more holistic understanding of reality than relying on a single interpretation. The plausibility of this argument is explained with a brief reference to the phenomenon of electron double-slit interference. The second part of the proposal asserts that, it is essential to eliminate any discrepancy between the way in which the terms ‘physics’ and ‘reality’ are regarded in scientific inquiry, for developing a universal, all-encompassing and consistent world view of the latter — emphasising that not only the ‘observed’ but also the ‘observer’ (considered here as the measuring instrument or apparatus) and the ‘Subject of Cognizance’ (viewed here as the conscious observer) are integral parts of the whole reality. This assertion is supported by some specific remarks of Richard Feynman and David Bohm.

In defence of Copenhagenism

The aim of the article is to analyze the ontological foundations of quantum mechanics and the relationship of various interpretations of quantum mechanics with the question of truth in scientific knowledge. The theoretical material (various interpretations of quantum mechanics) was analyzed. The research methods were analysis, comparative-historical and institutional approaches. On the basis of the study, it can be concluded that physicists are only able to predict the probabilities of physical phenomena or processes, without any knowledge of the structure of entity in itself. The study helps to complement the theoretical picture of the ontology of quantum mechanics and to get an idea about the development prospects of the methodology of physical sciences. We should not ascribe properties that are unobservable in experience to the entity because science can truly interpret only the representation of entity in itself in experience and the ways of dealing with it, not future events or possible states of the entity. Otherwise, science “slides” down to the level of dialectical (rhetorical) exercises based not on true premises, but on generally accepted or “authoritative” biases, which gives room to extreme forms of relativism and takes natural scientists away from studying nature to inventing empirically unsupported hypotheses. When, in accordance with the Cartesian ontology, the scientist assumes that the entity is as the “subject” observes it (that is, the “reflection” of the entity in consciousness is identified with entity in itself), this assumption leads the scientist to attempts to “scientifically” describe the future events or the possible states of the entity. The criterion for the truth of a scientific theory put forward by Einstein in his dispute with Bohr remains a fundamentally unattainable ideal. Cognition of nature is probabilistically and fundamentally incomplete since a person can consciously comprehend natural phenomena only within the framework of their representation in the existing being. The probabilistic nature of quantum mechanics is due to the impossibility of knowing things as they exist by themselves, that is, as they exist outside of representation in the mind of the observer. This does not mean that physical entities did not exist before their knowledge: they existed potentially, but were not valid for the observer, that is, conscious. Quantum physics is as incomplete as any other physical theory when compared with an unattainable ideal, but this fact does not negate its truth for modern scientists since quantum theory is based on the results of verified experiments.

The inadequacy of effective incoherence interpretations of quantum theory, as demonstrated by analysis of EPR measurements

The relationship between physics and phenomenology is a blind spot of current literature in a twofold sense. First, while many phenomenologists work on the interface to psychology, the cognitive sciences, biology, artificial intelligence, etc., only very few engage in phenomenological reflections on physics. This is puzzling since, as we shall see below, Husserl and other classical phenomenologists have been quite clear on the significance of such an undertaking, stressing the central role physics plays among the natural sciences. Secondly, while philosophy of physics has emerged as an important sub-discipline of philosophy in the twentieth century, there is hardly any work that addresses the role of phenomenology for the development of modern physics or the philosophical interpretation of physical theories (with notable exceptions that will be discussed below). This is puzzling since, as we shall see below, the father of modern field theory, Hermann Weyl, was inspired by phenomenological considerations when formulating his gauge principle, and there is a long (although usually unnoticed) history of phenomenological motifs in interpretations of quantum mechanics. Section 15.1 addresses the question of how to interpret physical theories and how to estimate the relationship between mathematical models and physical reality. In Sect. 15.2, we shed light on the perspectivist features of Husserl’s philosophy of science and discuss how it relates to current versions of scientific perspectivism. Section 15.3 addresses how phenomenological ideas have influenced the development and interpretation of early modern physics. In Sect. 15.4, we discuss observer-dependence in modern physics and highlight phenomenological motifs in Wheeler’s conception of “observer-participancy.” Finally, Sect. 15.5 sheds light on phenomenological motifs in a novel interpretation of quantum mechanics, namely QBism, and emphasizes similarities between phenomenology and the program of reconstructing quantum mechanics, a program that currently enjoys popularity in the field of quantum foundations. We shall see that the worldviews delivered by phenomenology and physics might be closer than is commonly assumed.

CONCEPTUAL FOUNDATIONS OF QUANTUM MECHANICS: THE ROLE OF EVIDENCE THEORY, QUANTUM SETS, AND MODAL LOGIC

Frauchiger and Renner have recently claimed to prove that “Single-world interpretations of quantum theory cannot be self-consistent”. This is contradicted by a construction due to Bell, inspired by Bohmian mechanics, which shows that any quantum system can be modelled in such a way that there is only one “world” at any time, but the predictions of quantum theory are reproduced. This Bell–Bohmian theory is applied to the experiment proposed by Frauchiger and Renner, and their argument is critically examined. It is concluded that it is their version of “standard quantum theory”, incorporating state vector collapse upon measurement, that is not self-consistent.

As always, Albert Einstein was ahead of his time. Quantum theory was still in its infancy, its formalism a mere sketch, and its implications only beginning to be realized. Yet Einstein, in 1917, already spotted what would trouble him throughout his lifetime. He concluded that the nascent theory, which he had helped initiate, seemed to leave “time and direction of elementary processes,” such as the spontaneous emission of radiation from a molecule, “to chance” [1]. Einstein’s conclusion was visionary. It was also incredibly bold, for it suggested a radical departure from the powerful, centuries-old deterministic and causal worldview of classical physics. But Einstein also immediately expressed his discomfort with the idea of fundamental chance. In fact, his worries were just the seed of what would turn into one of the longest and most heated debates in the history of physics. What does quantum theory mean, and what does it tell us about the nature of reality? Some of the brightest minds in physics locked horns over these issues. Besides Einstein, there were Niels Bohr, Erwin Schrodinger, Werner Heisenberg, Pascual Jordan, Carl Friedrich von Weizsacker, Wolfgang Pauli, and Richard Feynman, just to name a few. Ask anyone today working on foundational questions in quantum theory and you are likely to hear that there is still no consensus on many of these questions—all the while, of course, everybody seems to be in perfect agreement on how to apply the quantum formalism when it comes to making experimental predictions. Remarkably, there has never been any serious attempt to find out what the current opinions of the community really are and how

Klein-Weyl's program and the ontology of gauge and quantum systems

Can Bohmian trajectories account for quantum recurrences having classical periodicities?

Quantum processes on phase space