There is no measurement problem for Humeans

The measurement problem concerns an apparent conflict between the two fundamental principles of quantum mechanics, namely the Schrödinger equation and the measurement postulate. These principles describe inconsistent behavior for quantum systems in so-called “measurement contexts.” Many theorists have thought that the measurement problem can only be resolved by proposing a mechanistic explanation of (genuine or apparent) wavefunction collapse that avoids explicit reference to “measurement.” However, I argue here that the measurement problem dissolves if we accept Humeanism about laws of nature. On a Humean metaphysics, there is no conflict between the two principles, nor is there any inherent problem with the concept of “measurement” figuring into the account of collapse.     

GRW and the tails problem

The GRW theory is a recent attempt to solve the measurement problem in quantum mechanics, and the tails problem is a well-known and potentially fatal criticism of the GRW theory. The first half of the paper is an exposition of the measurement problem, the GRW theory, and the tails problem. In the remainder of the paper, two methods of dealing with the tails problem are considered: first, altering the GRW theory so as to avoid the tails problem; and second, denying that the tails problem is more than a novel aspect of a universal vagueness in the way scientific theories relate to everyday language.     

Axiomatic quantum mechanics and radioactive decay

This paper explores the consequences of the orthodox resolution of the measurement problem for the axiomatic base of non-relativistic elementary quantum mechanics. It is argued that the standard resolution of the measurement problem generates a paradox whose dissolution may be achieved through an enrichment of the axiomatic foundations of quantum mechanics. These results are also linked to some recent creative proposals by Nancy Cartwright concerning the nature of the so-called reduction of the wave packet.     

Response to Stuart Kauffman: The Measurement Problem in Quantum Mechanics

Richard Feynman, a 1965 Nobel Prize winner in physics, quoting an unknown philosopher, said: “It is necessary for the very existence of science that the same conditions always produce the same results.” And Feynman's reply: “Well, they don't.” Double-slit experiments with both slits open and the wave interference pattern created by electrons falling on a screen behind the slits speak volumes to those two statements and the interpretive problem created by the non-deterministic behavior of microscopic matter. Quantum mechanics (QM) with its successes over the last 85 years has created the information age, and with insights into nature has given humans an economy concentrated with products based on quantum technology. All this even with questions about the fundamental aspects of measurement in the quantum world still being debated! Discussing the measurement aspect of QM does not require a physics background where physics scholars join other scholarly disciplines engaged in gaining knowledge about the reality of the one world of human experience. The necessary tools for discussion are imagination, speculation, and curiosity. But for a new credible interpretation of the measurement problem, quantum training or a quantum theoretician is required.     

Measurement and Indeterminacy in the Quantum Mechanics of Dirac

The quantum-measurement problem and the Heisenberg indeterminacy principle are presented in the language of the Dirac formulation of the quantum theory. Particularly the relationship between quantum state prior to measurement and the result of the measurement are discussed. The relation between the indeterminacy principle and the analog between quantum and classical systems is presented, showing that this principle may be discussed independently of the wave-particle duality. The importance of statistics in the treatment of many body systems is outlined and the approach to investigating God's interaction with human beings is discussed in this context. The treatment is nonmathematical.     

Scientific Realism and Quantum Mechanics: Revisiting a Controversial Relation

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.     

The measurement problem revisited

Synthese - It has been realized that the measurement problem of quantum mechanics is essentially the determinate-experience problem, and in order to solve the problem, the physical state...     

A Quantum-Mechanical Argument for Mind–Body Dualism

I argue that a strong mind–body dualism is required of any formulation of quantum mechanics that satisfies a relatively weak set of explanatory constraints. Dropping one or more of these constraints may allow one to avoid the commitment to a mind–body dualism but may also require a commitment to a physical–physical dualism that is at least as objectionable. Ultimately, it is the preferred basis problem that pushes both collapse and no-collapse theories in the direction of a strong dualism in resolving the quantum measurement problem. Addressing this problem illustrates how the construction and evaluation of explanatorily rich physical theories are inextricably tied to the evaluation of traditional philosophical issues.     

Quantum theory and the relation between the conscious mind and the physical world

The measurement problem of quantum theory is discussed, and the difficulty of trying to solve it within the confines of a local, Lorentz-invariant physics is emphasised. This leads to the obvious suggestion to seek a solution beyond physics, in particular, by introducing the concept of consciousness. The resulting dualistic model, in the natural form suggested by quantum theory, is shown to differ in several respects from the classical model of Descartes, and to suggest solutions to some of the long-standing problems concerning the relation of consciousness to the physical world.     

Divine Action and Quantum Theory

Recent articles by Nicholas Saunders, Carl Helrich, and Jeffrey Koperski raise important questions about attempts to make use of quantum mechanics in giving an account of particular divine action in the world. In response, I make two principal points. First, some of the most pointed theological criticisms lose their force if we attend with sufficient care to the limited aims of proposals about divine action at points of quantum indetermination. Second, given the current state of knowledge, it remains an open option to make theological use of an indeterministic interpretation of quantum mechanics. Any such proposal, however, will be an exploratory hypothesis offered in the face of deep uncertainties regarding the measurement problem and the presence in natural systems of amplifiers for quantum effects.     

Can the Decoherence Approach Help to Solve the Measurement Problem?

This work examines whether the environmentally-induced decoherence approach in quantum mechanics brings us any closer to solving the measurement problem, and whether it contributes to the elimination of subjectivism in quantum theory. A distinction is made between ,collapse, and ,decoherence,, so that an explanation for decoherence does not imply an explanation for collapse. After an overview of the measurement problem and of the open-systems paradigm, we argue that taking a partial trace is equivalent to applying the projection postulate. A criticism of Zurek's decoherence approach to measurements is also made, based on the restriction that he must impose on the interaction between apparatus and environment. We then analyze the element of subjectivity involved in establishing the boundary between system and environment, and criticize the incorporation of Everett's branching of memory records into the decoherence research program. Sticking to this program, we end by sketching a proposal for ‘environmentally-induced collapse’. This revised version was published online in June 2006 with corrections to the Cover Date.     

The problem of properties in quantum mechanics

The properties of classical and quantum systems are characterized by different algebraic structures. We know that the properties of a quantum mechanical system form a partial Boolean algebra not embeddable into a Boolean algebra, and so cannot all be co-determinate. We also know that maximal Boolean subalgebras of properties can be (separately) co-determinate. Are there larger subsets of properties that can be co-determinate without contradiction? Following an analysis of Bohrs response to the Einstein-Podolsky-Rosen objection to the complementarity interpretation of quantum mechanics, a principled argument is developed justifying the selection of particular subsets of properties as co-determinate for a quantum system in particular physical contexts. These subsets are generated by sets of maximal Boolean subalgebras, defined in each case by the relation between the quantum state and a measurement (possibly, but not necessarily, the measurement in terms of which we seek to establish whether or not a particular property of the system in question obtains). If we are required to interpret quantum mechanics in this way, then predication for quantum systems is quite unlike the corresponding notion for classical systems.     

Time as non‐observational knowledge: How to straighten out ΔEΔt≥h

The Energy‐Time Uncertainty (ETU) has always been a problem‐ridden relation, its problems stemming uniquely from the perplexing question of how to understand this mysterious Δt. On the face of it (and, indeed, far deeper than that), we always know what time it is. Few theorists were ignorant of the fact that time in quantum mechanics is exogenously defined, in no ways intrinsically related to the system. Time in quantum theory is an independent parameter, which simply means independently known. In the early 1960s Aharonov (1961–64) and Bohm (1961–64) mounted a spirited attack against the ETU, which sealed its fate to the present date. By emphasising that time is always “well‐defined” in quantum theory, they were led to the conclusion that no ETU should exist, a view shared by many in the 1990s, if Busch (1990) is to be believed. In a similar vein, I emphasize that (a) physical systems occupy a particular energy state at a particular instant of time, if at all; (b) even in absence of all time‐measuring instruments, it is still trivially warranted that one can measure a system's energy as accurately as one pleases, and simply announce “The system's energy is exactly E NOW!”, a possibility which no quantum mechanics of any sort, or any physical theory whatsoever, can afford to tamper with or change, except circularly. One never loses one's own perception of time, when one measures the energy, a fact which no measurement conceivable can interfere with or affect. Both (a) and (b) uniquely entail that energy and time are compatible, if not indeed intimately interconnected, contrary to what the relevant uncertainty seems to affirm. In response to Aharonov's and Bohm's initial problem, I reinterpret ΔEΔt ≥ h, as directly derived from authentic quantum principles, without however having to assume a direct incompatibility between its related concepts, attributing their complementarity to conditions other than ordinarily assumed.     

Weak Discernibility in Quantum Mechanics: Does It Save PII?

The Weak Principle of the Identity of Indiscernibles (weak PII), states that numerically distinct items must be discernible by a symmetrical and irreflexive relation. Recently, some authors have proposed that weak PII holds in non relativistic quantum mechanics, contradicting a long tradition claiming PII to be simply false in that theory. The question that arises then is: are relations allowed in the scope of PII? In this paper, we propose that quantum mechanics does not help us in deciding matters concerning that problem, since that is a metaphysical problem rather than a quantum mechanical one. We argue further that weak PII is unmotivated on metaphysical grounds. We examine three metaphysical theses (bundle theory, counting, empiricism) that may provide reasons for one to sustain PII, and we conclude that weak PII gets no independent motivation from them.     

Measurement as transcendental–empirical <Emphasis Type="Italic">écart</Emphasis>: Merleau-Ponty on deep temporality

Merleau-Ponty’s radical reflection conceptualizes the transcendental and the empirical as intertwined, emerging only via an écart. I advance this concept of transcendental empirical écart by studying the problem of measurement in science, in both general and quantum mechanical contexts. Section one analyses scientific problems of measurement, focusing on issues of temporality, to show how measurement entails a transcendental that diverges with the empirical. Section two briefly interprets this result via Merleau-Ponty’s concept of depth, to indicate how measurement reveals a temporality that is not an already given ground that would guarantee the transcendental in advance: temporality is instead ‘deep,’ itself engendering a divergence of transcendental and empirical operations that first allows for measurement and sense.     

ON THE APPLICABILITY OF THE QUANTUM MEASUREMENT FORMALISM

Customary discussions of quantum measurements are unrealistic, in the sense that they do not reflect what happens in most actual measurements even under ideal circumstances. Even theories of measurement which discard the projection postulate tend to retain two unrealistic assumptions of the von Neumann theory: that a measurement consists of a single physical interaction, and that the topic of every measurement is information wholly contained in the quantum state of the object of measurement. I suggest that these unrealistic assumptions originate from an overly literal interpretation of the operator formalism of quantum mechanics. I also suggest, following Park, that some issues can be clarified by distinguishing the sense of the term 'measurement' occurring in the quantum-mechanical operator formalism, and the sense of 'measurement' that refers to actual processes of gaining information about the physical world.     

The suggestive properties of quantum mechanics without the collapse postulate

Everett proposed resolving the quantum measurement problem by dropping the nonlinear collapse dynamics from quantum mechanics and taking what is left as a complete physical theory. If one takes such a proposal seriously, then the question becomes how much of the predictive and explanatory power of the standard theory can one recover without the collapse postulate and without adding anything else. Quantum mechanics without the collapse postulate has several suggestive properties, which we will consider in some detail. While these properties are not enough to make it acceptable given the usual standards for a satisfactory physical theory, one might want to exploit these properties to cook up a satisfactory no-collapse formulation of quantum mechanics. In considering how this might work, we will see why any no-collapse theory must generally fail to satisfy at least one of two plausible-sounding conditions.     

Does God Cheat at Dice? Divine Action and Quantum Possibilities

The recent debates concerning divine action in the context of quantum mechanics are examined with particular reference to the work of William Pollard, Robert J. Russell, Thomas Tracy, Nancey Murphy, and Keith Ward. The concept of a quantum mechanical "event" is elucidated and shown to be at the center of this debate. An attempt is made to clarify the claims made by the protagonists of quantum mechanical divine action by considering the measurement process of quantum mechanics in detail. Four possibilities for divine influence on quantum mechanics are identified and the theological and scientific implications of each discussed. The conclusion reached is that quantum mechanics is not easily reconciled with the doctrine of divine action.