Abstract Quantum decoherence is receiving a great deal of attention today not only in theoretical and experimental physics but also in branches of science as diverse as molecular biology, biochemistry, and even neuropsychology. It is no surprise that it is also beginning to appear in various philosophical debates concerning the fundamental structure of the world. The purpose of this article is primarily to acquaint non‐specialists with quantum decoherence and clarify related concepts, and secondly to sketch its possible implications – independent of particular interpretations of quantum mechanics – for broader philosophical debates. For example, decoherence shows that any method of parsing nature into levels or parts cannot be in principle but instead derives from our perception of the world as classical, a perception that is itself sustained by the process of decoherence.
Abstract Quantum decoherence is receiving a great deal of attention today not only in theoretical and experimental physics but also in branches of science as diverse as molecular biology, biochemistry, and even neuropsychology. It is no surprise that it is also beginning to appear in various philosophical debates concerning the fundamental structure of the world. The purpose of this article is primarily to acquaint non‐specialists with quantum decoherence and clarify related concepts, and secondly to sketch its possible implications – independent of particular interpretations of quantum mechanics – for broader philosophical debates. For example, decoherence shows that any method of parsing nature into levels or parts cannot be in principle but instead derives from our perception of the world as classical, a perception that is itself sustained by the process of decoherence.
Introduction Chapter 1 dealt with one of the deepest mysteries in modern science: how to explain consciousness. This Part deals with another mystery: how to make sense of quantum mechanics. Both involve a problem of reconciliation with the classical worldview, which is one hint that the two mysteries might be related. A second is that, unlike classical physics, which makes no reference to or allowance for consciousness, quantum theory raises the issue of consciousness and its relationship to the physical world in a very direct way. These hints do not necessarily mean there is a connection between the two mysteries, but by the end of this Part I hope to have shown why it would be natural to look for one. My more immediate aim here is to give the social scientific reader an introductory understanding of the experimental findings of quantum theory, its key concepts, and the debates about its interpretation. The discussion assumes no prior knowledge of quantum physics and makes no use of mathematics. Quantum theory without equations might seem like an oxymoron, and certainly reading this Part will not enable anyone to use quantum theory. But to a perhaps surprising degree it is possible to understand quantum theory without being able to use it. Its findings can be communicated in ordinary language, and the same goes for its main concepts and interpretive debates. One consequence of this has been the emergence of a virtual cottage industry of books on quantum theory for a lay audience. Most are written by physicists, and many are quite good. However, it is not just popular treatments that do without equations: much of the professional philosophical literature does as well. (I draw on both kinds of literature below.) Philosophers of physics are trained to understand the math, of course, which is necessary for a full appreciation of the issues.
Quantum decoherence is a dynamical process whereby a system's phase relations become delocalized due to interaction and subsequent entanglement with its environment. This delocalization, or decoherence, forces the quantum system into a state that is apparently classical (or apparently an eigenstate) by prodigiously suppressing features that typically give rise to so-called quantum behavior. Thus it has been frequently proposed by physicists and philosophers alike that decoherence explains the dynamical transition from quantum behavior to classical behavior. Statements like this assume the existence of distinct realms, however, and the present thesis is an exploration of the metaphysical consequences of quantum decoherence motivated by the question of the quantum-to-classical transition and interlevel relations: if there are in-principle ``classical' and ``quantum' levels, what are the relations between them? And if there are no such levels, what follows? Importantly, the following philosophical investigations are carried out by intentionally leaving aside the measurement problem and concerns about particular interpretations of quantum mechanics. Good philosophical work, it is argued, can be done without adopting a specific interpretational framework and without recourse to the measurement problem. After introducing the physics of decoherence and exploring the four canonical models applied to system-environment interactions, it is argued that, ontologically speaking, there exist no levels. This claim--called the ``nontological thesis'--exposes as ill-posed questions regarding the transition from the quantum regime to the classical regime and reveals the inappropriateness of interlevel relations (like reduction, supervenience and emergence) operating within metaphysical frameworks. The nontological thesis has further important consequences regarding intralevel relations: not only are there no meaningful ways to carve the world into levels, but there are no meaningful ways to carve the world into parts and wholes either. These conclusions, supported by quantum decoherence and the empirical success of its models, drastically alter the philosophical terrain--not just in physics or in the philosophy of physics, but in traditional metaphysics as well.
The complex relation between quantum mechanics and classical mechanics is crucial in the philosophy of modern physics, and it cuts across current quantum physics. This paper is divided in two parts. In the first part I will offer a critical analysis of the role that decoherence plays in the account of the quantum-classical limit. In the second part I will mention three ways in which philosophers are engaging with the realist interpretation of quantum mechanics in light of the assessment that the problem of the quantum-classical limit is still open to debate. My main claim is that the problem of the quantum-classical limit is overrated and it receives too much attention for the realist who looks at quantum mechanics. The question that the realist wants to focus on is the crucial interpretation question: what is a quantum system?
Quantum theory underpins much of modern physics and its implications draw the attention of industry, academia and public funding agencies. However there are many unsettled conceptual and philosophical problems in the interpretation of quantum mechanics which are a matter of extensive debate. These hotly debated topics include the meaning of the wave function, the nature of the quantum objects, the role of the observer, the non-locality of the quantum world, and the emergence of classicality from the quantum domain. Containing chapters written by eminent researchers from the fields of physics and philosophy, this book provides interdisciplinary, comprehensive and up-to-date perspectives of the problems related to the interpretation of quantum theory. It is ideal for academic researchers in physics and philosophy working on the ontology of quantum mechanics.
Quantum mechanics, a cornerstone of modern physics, elucidates the behavior of particles at the most fundamental level. This paper delves into the foundational aspects and diverse interpretations of quantum mechanics, shedding light on its enigmatic principles and implications. Beginning with a comprehensive overview of the mathematical framework underlying quantum mechanics, including wave functions, operators, and probabilistic interpretations, the study explores key foundational principles such as superposition, uncertainty, and entanglement. Moreover, it critically examines various interpretations of quantum mechanics, including the Copenhagen interpretation, many-worlds interpretation, and pilot-wave theory, elucidating their philosophical underpinnings and empirical consequences. Through a synthesis of theoretical analysis and empirical evidence, this paper navigates the intricate landscape of quantum mechanics, offering insights into its profound implications for our understanding of reality.
Abstract Metaphysicians should pay attention to quantum mechanics, but not because it provides definitive answers to many metaphysical questions. The theory itself is remarkably silent on the nature of the physical world, and the various interpretations of the theory on offer present conflicting ontological pictures. Rather, quantum mechanics is essential to the metaphysician because it reshapes standard metaphysical debates and opens up unforeseen new metaphysical possibilities. Even if quantum mechanics provides few clear answers, there are good reasons to think that any adequate understanding of the quantum world will result in a radical reshaping of our classical worldview in some way or other. Whatever the world is like at the atomic scale, it is almost certainly not the swarm of particles pushed around by forces that is often presupposed. This book guides readers through the theory of quantum mechanics and its implications for metaphysics in a clear and accessible way. The theory and its various interpretations are presented with a minimum of technicality. The consequences of these interpretations for metaphysical debates concerning realism, indeterminacy, causation, determinism, holism, and individuality (among other topics) are explored in detail, stressing the novel form that the debates take given the empirical facts in the quantum domain. While quantum mechanics may not deliver unconditional pronouncements on these issues, the range of possibilities consistent with our knowledge of the empirical world is relatively small—and each possibility is metaphysically revisionary in some way.