interpretations of quantum mechanics (stanford)
Although quantum mechanics has held up to rigorous and extremely precise tests in an extraordinarily broad range of experiments (not one prediction from quantum mechanics has been found to be contradicted by experiments), there exist a number of contending schools of thought over their interpretation. Realism is also a property of each of the elements of the maths; an element is real if it corresponds to something in the interpreting structure. In order for this to make sense, measurement operations in the interpreting structure must be localized. For example, in this interpretation, a quantum state is not an element of reality—instead it represents the degrees of belief an agent has about the possible outcomes of measurements. Cit. Quantum mechanics is regarded as a way of predicting observations, or a theory of measurement. However, this term now is used to describe a larger set of models that grew out of this approach. To that extent, the physical theory stands, and is consistent with itself and with reality; difficulties arise only when one attempts to "interpret" the theory. Other approaches to resolve conceptual problems introduce new mathematical formalism, and so propose alternative theories with their interpretations. (2006). To hide this material, click on the Teacher or Normal link. BST has applications to Bell's theorem, quantum computation and quantum gravity. The theory is based on a consistency criterion that allows the history of a system to be described so that the probabilities for each history obey the additive rules of classical probability. ...A quantum mechanical state being a summary of the observer's information about an individual physical system changes both by dynamical laws, and whenever the observer acquires new information about the system through the process of measurement. It also has some resemblance to hidden-variable theories and the ensemble interpretation: particles in BST have multiple well defined trajectories at the microscopic level. Examples include, In his treatise The Mathematical Foundations of Quantum Mechanics, John von Neumann deeply analyzed the so-called measurement problem. [17][10] They subdivide into two kinds. These views on interpretation differ on such fundamental questions as whether quantum mechanics is deterministic or stochastic, which elements of quantum mechanics can be considered real, and what is the nature of measurement, among other matters. For instance, Erwin Schrödinger originally viewed the electron's wave function as its charge density smeared across space, but Max Born reinterpreted the absolute square value of the wave function as the electron's probability density distributed across space. The value returned by a measurement corresponds to the value of some function in the state space. [14] In that paper the authors proposed the concepts element of reality and the completeness of a physical theory. Interpretations where quantum mechanics is said to describe an observer's knowledge of the world, rather than the world itself. QBism draws from the fields of quantum information and Bayesian probability and aims to eliminate the interpretational conundrums that have beset quantum theory. [15] In general, after a measurement (click of a Geiger counter or a trajectory in a spark or bubble chamber) it ceases to be relevant unless subsequent experimental observations can be performed. ", http://www.naturalthinker.net/trl/texts/Heisenberg,Werner/Heisenberg,%20Werner%20-%20Physics%20and%20philosophy.pdf, "Quantum physics has been rankling scientists for decades". Moreover, to know the motion of the particles at any moment, you have to know what the Markov process is. Bell's theorem, combined with experimental testing, restricts the kinds of properties a quantum theory can have, the primary implication being that quantum mechanics cannot satisfy both the principle of locality and counterfactual definiteness. The Role of Observership in Quantum Theory", "Why Bohm's Theory Solves the Measurement Problem", "Review of Penrose's Shadows of the Mind", "Modal Interpretations of Quantum Mechanics", Sharlow, Mark; "What Branching Spacetime might do for Physics", "Nonlocal Position Changes of a Photon Revealed by Quantum Routers", International Encyclopedia of Unified Science, Copenhagen Interpretation of Quantum Mechanics, Everett's Relative State Formulation of Quantum Mechanics, Many-Worlds Interpretation of Quantum Mechanics, Modal Interpretation of Quantum Mechanics, Quantum-Bayesian and Pragmatist Views of Quantum Theory, The Role of Decoherence in Quantum Mechanics, Everettian Interpretations of Quantum Mechanics, https://en.wikipedia.org/w/index.php?title=Interpretations_of_quantum_mechanics&oldid=982265240, Wikipedia articles needing factual verification from July 2019, Creative Commons Attribution-ShareAlike License. In a semantic view of interpretation, an interpretation is complete if every element of the interpreting structure is present in the mathematics. It is no more real than a probability distribution is in. Quantum Darwinism is a theory meant to explain the emergence of the classical world from the quantum world as due to a process of Darwinian natural selection induced by the environment interacting with the quantum system; where the many possible quantum states are selected against in favor of a stable pointer state. "Physics concerns what we can say about nature". Citation for this page in APA citation style. An interpretation of quantum mechanics is an attempt to explain how the mathematical theory of quantum mechanics "corresponds" to reality. The transactional interpretation is explicitly non-local. A realist stance seeks the epistemic and the ontic, whereas an antirealist stance seeks epistemic but not the ontic. Despite nearly a century of debate and experiment, no consensus has been reached among physicists and philosophers of physics concerning which interpretation best "represents" reality.[1][2]. An entirely classical derivation and interpretation of Schrödinger's wave equation by analogy with Brownian motion was suggested by Princeton University professor Edward Nelson in 1966. This research area and its name originated in the 1936 paper by Garrett Birkhoff and John von Neumann, who attempted to reconcile some of the apparent inconsistencies of classical boolean logic with the facts related to measurement and observation in quantum mechanics. (1963). Introduction-- Part I. (Cambridge University, Cambridge, 1987) p. 194. van Kampen, N. G. (2008). 6. Information ontologies, such as J. In these theories, a single measurement cannot fully determine the state of a system (making them a type of hidden-variables theory), but given two measurements performed at different times, it is possible to calculate the exact state of the system at all intermediate times. Stanford Libraries' official online search tool for books, media, journals, databases, government documents and more. A brief introduction to some of the different approaches to the difficult problem of understanding what quantum mechanics really means! In the words of Einstein: The attempt to conceive the quantum-theoretical description as the complete description of the individual systems leads to unnatural theoretical interpretations, which become immediately unnecessary if one accepts the interpretation that the description refers to ensembles of systems and not to individual systems. Particles, which always have positions, are guided by the wavefunction. According to the Copenhagen interpretation, the wavefunction collapses when a measurement is performed. "[58] This position is not uncommon among practitioners of quantum mechanics. Lamb, W. E. (2001). Thus, objective-collapse theories are realistic, indeterministic, no-hidden-variables theories. Observers separate the universal wavefunction into orthogonal sets of experiences. A phenomenon can receive interpretation either ontic or epistemic. The current usage of realism and completeness originated in the 1935 paper in which Einstein and others proposed the EPR paradox. He concluded that the entire physical universe could be made subject to the Schrödinger equation (the universal wave function). Am. 69: 413-421. mathematical structure of quantum mechanics, Leibniz's Principle of the identity of indiscernibles, Minority interpretations of quantum mechanics, Philosophical interpretation of classical physics, https://www.youtube.com/watch?v=f-OFP5tNtMY, https://www.youtube.com/watch?v=72us6pnbEvE, "Constructing the Myth of the Copenhagen Interpretation", http://plato.stanford.edu/entries/qm-manyworlds/#Teg98, "Commentary: Quantum mechanics: Fixing the shifty split", The role of decoherence in quantum mechanics, "Can quantum-mechanical description of physical reality be considered complete? The phenomena associated with measurement are claimed to be explained by decoherence, which occurs when states interact with the environment producing entanglement, repeatedly "splitting" the universe into mutually unobservable alternate histories—effectively distinct universes within a greater multiverse. "The scandal of quantum mechanics". Heisenberg and Bohr: divergent viewpoints of complementarity-- Part III. [10] This interpretation is distinguished by its use of a subjective Bayesian account of probabilities to understand the quantum mechanical Born rule as a normative addition to good decision-making. Consequently, if quantum mechanics is to be a complete theory, relational quantum mechanics argues that the notion of "state" describes not the observed system itself, but the relationship, or correlation, between the system and its observer(s). An interpretation of quantum mechanics is an attempt to explain how the mathematical theory of quantum mechanics "corresponds" to reality. It was proposed in 2003 by Wojciech Zurek and a group of collaborators including Ollivier, Poulin, Paz and Blume-Kohout. Interpretation of quantum mechanics. The views of several early pioneers of quantum mechanics, such as Niels Bohr and Werner Heisenberg, are often grouped together as the "Copenhagen interpretation", though physicists and historians of physics have argued that this terminology obscures differences between the views so designated. The many-worlds interpretation is an interpretation of quantum mechanics in which a universal wavefunction obeys the same deterministic, reversible laws at all times; in particular there is no (indeterministic and irreversible) wavefunction collapse associated with measurement.
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