The Quantum Measurement Problem

2019 ◽  
pp. 105-117
Author(s):  
Jeffrey A. Barrett
Keyword(s):  
Quantum Mechanics ◽  
Quantum Measurement ◽  
Physical System ◽  
Measurement Problem ◽  
Standard Theory ◽  
Standard Formulation ◽  
Logical Consistency ◽  
Quantum Measurement Problem ◽  
Logical Inconsistency ◽  
Wigner’S Friend

We use the Wigner’s friend story to characterize the quantum measurement problem. On the standard formulation of quantum mechanics, whether a physical system is measured determines which of the theory's two dynamical laws obtains. For this reason, the logical consistency of the theory depends on one specifying strictly disjoint conditions for when when each law obtains, which means that one needs to say precisely what constitutes a measurement. But since the term measurement occurs in the standard theory as an undefined primitive term, the theory is at best incomplete. We see precisely how this conceptual incompleteness threatens the logical inconsistency of the theory and why, on even the most charitable reading, it entails that the theory is empirical incomplete. We end by considering why its empirically incompleteness is extremely difficult to test.

scholarly journals Decoherence and its role in the modern measurement problem

2012 ◽  
Vol 370 (1975) ◽  
pp. 4576-4593 ◽  
Author(s):  
David Wallace
Keyword(s):  
Wave Function ◽  
Quantum Mechanics ◽  
Quantum Measurement ◽  
Measurement Problem ◽  
Scientific Practice ◽  
Measurement Theory ◽  
Quantum Measurements ◽  
Quantum Measurement Problem ◽  
Modern Physics ◽  
Conceptual Problems

Decoherence is widely felt to have something to do with the quantum measurement problem, but getting clear on just what is made difficult by the fact that the ‘measurement problem’, as traditionally presented in foundational and philosophical discussions, has become somewhat disconnected from the conceptual problems posed by real physics. This, in turn, is because quantum mechanics as discussed in textbooks and in foundational discussions has become somewhat removed from scientific practice, especially where the analysis of measurement is concerned. This paper has two goals: firstly (§§1–2), to present an account of how quantum measurements are actually dealt with in modern physics (hint: it does not involve a collapse of the wave function) and to state the measurement problem from the perspective of that account; and secondly (§§3–4), to clarify what role decoherence plays in modern measurement theory and what effect it has on the various strategies that have been proposed to solve the measurement problem.

scholarly journals Measured distribution of cloud chamber tracks from radioactive decay: a new empirical approach to investigating the quantum measurement problem

2021 ◽  
Author(s):  
Jonathan Schonfeld
Keyword(s):  
Spatial Distribution ◽  
Quantum Mechanics ◽  
Quantum Measurement ◽  
Measurement Problem ◽  
Radioactive Decay ◽  
Foundations Of Quantum Mechanics ◽  
Radioactive Source ◽  
Cloud Chamber ◽  
Quantum Measurement Problem ◽  
Measured Distribution

Abstract Using publically available video of a cloud chamber with a very small radioactive source, I measure the spatial distribution of where tracks start, and consider possible implications. This is directly relevant to the quantum measurement problem and its possible resolution, and appears never to have been done before. The raw data are relatively uncontrolled, leading to caveats that should guide future, more tailored experiments. Track distributions from decays in cloud chambers represent a previously unappreciated way to probe the foundations of quantum mechanics, and a novel case of wavefunctions with macroscopic signatures.

The Collapse of the Quantum State

2019 ◽  
pp. 118-142
Author(s):  
Jeffrey A. Barrett
Keyword(s):  
Quantum Mechanics ◽  
Quantum State ◽  
Quantum Measurement ◽  
Measurement Problem ◽  
Primitive Ontology ◽  
Quantum Measurement Problem

We consider Wigner’s proposal for solving the quantum measurement problem. His solution involves a strong mind-body dualism, but it is also possible to provide a purely physical collapse solution to the quantum measurement problem. To this end, we consider the GRW formulation of quantum mechanics and three ways one might interpret it: GRWr, GRWm, and GRWf. These ways of interpreting the theory differ in the metaphysical commitments one makes and, hence, in how one explains one’s measurement records and hence one’s experience. This provides an introduction to the notions of an empirical ontology and a primitive ontology. We consider some of the comparative virtues and vices of the GRW formulation of quantum mechanics.

scholarly journals Interpretive analogies between quantum and statistical mechanics

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
C. D. McCoy
Keyword(s):  
Quantum Mechanics ◽  
Statistical Mechanics ◽  
Quantum Measurement ◽  
Measurement Problem ◽  
Initial Conditions ◽  
Primitive Ontology ◽  
Quantum Measurement Problem ◽  
Classical Statistical Mechanics ◽  
Interpretive Strategies ◽  
Significant Application

AbstractThe conspicuous similarities between interpretive strategies in classical statistical mechanics and in quantum mechanics may be grounded on their employment of common implementations of probability. The objective probabilities which represent the underlying stochasticity of these theories can be naturally associated with three of their common formal features: initial conditions, dynamics, and observables. Various well-known interpretations of the two theories line up with particular choices among these three ways of implementing probability. This perspective has significant application to debates on primitive ontology and to the quantum measurement problem.

Quantum Interference

2019 ◽  
pp. 66-88
Author(s):  
Jeffrey A. Barrett
Keyword(s):  
Hilbert Space ◽  
Wave Function ◽  
Quantum Mechanics ◽  
Quantum Interference ◽  
Standard Theory ◽  
Quantum Decoherence ◽  
Entangled States ◽  
Quantum Mechanical ◽  
Standard Formulation ◽  
Complex Valued

Moving to more subtle experiments, we consider how the standard formulation of quantum mechanics predicts and explains interference phenomena. Tracking the conditions under which one observes interference phenomena leads to the notion of quantum decoherence. We see why one must sharply distinguish between collapse phenomena and decoherence phenomena on the standard formulation of quantum mechanics. While collapses explain determinate measurement records, environmental decoherence just produces more complex, entangled states where the physical systems involved lack ordinary physical properties. We characterize the quantum-mechanical wave function as both an element of a Hilbert space and a complex-valued function over a configuration space. We also discuss how the wave function is interpreted in the standard theory.

scholarly journals ENTANGLEMENT QUANTISTICO

2020 ◽  
Author(s):  
Alberto Rimini
Keyword(s):  
Wave Function ◽  
Quantum Mechanics ◽  
Quantum Measurement ◽  
First Principles ◽  
Measurement Problem ◽  
Entangled State ◽  
Uncertainty Relations ◽  
Entanglement State ◽  
State Uncertainty ◽  
Einstein Podolsky Rosen

This extended note deals with a pedagogical description of the entangled state of two particles, starting from first principles. After some general remarks about quantum mechanics and physical theories, the single particle case is discussed by defining state, uncertainty relations and wave function in the state space. The system of two particles is then considered, with its possible states, starting from the original papers by Einstein Podolsky Rosen and by Schroedinger. The quantum measurement problem is then introduced, together with its role in the entanglement state. Finally the orthodox solution and the relevant conclusions are drawn.

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