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Revision as of 09:50, 15 February 2006 by 217.19.78.69 (talk) (→Indeterminacy and incompleteness)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Quantum indeterminacy is the apparent necessary incompleteness in the description of a physical system, that has become one of the characteristics of the standard description of quantum physics. Prior to quantum physics, it was thought that (a) a physical system had a determinate state which uniquely determined all the values of its measurable properties, and conversely (b) the values of its measurable properties uniquely determined the state. Albert Einstein may have been the first person to carefully point out the radical effect the new quantum physics would have on our notion of physical state.
Quantum indeterminacy can be quantitatively characterized by a probability distribution on the set of outcomes of measurements of an observable. The distribution is uniquely determined by the system state, and moreover quantum mechanics provides a recipe for calculating this probability distribution.
Indeterminacy in measurement was not an innovation of quantum mechanics, since it had established early on by experimentalists that errors in measurement may lead to indeterminate outcomes. However, by the latter half of the eighteenth century, measurement errors were well understood and it was known that they could either reduced by better equipment or accounted for by statistical error models. In quantum mechanics, however indeterminacy is of a much more fundamental nature, having nothing to do with errors or disturbance.
External link
- Common Misconceptions Regarding Quantum Mechanics See especially part III "Misconceptions regarding measurement".
References
- A. Aspect, Bell's inequality test: more ideal than ever, Nature 398 189 (1999).
- V. Braginski and F. Khalili, Quantum Measurements, Cambridge University Press, 1992.
- G. Bergmann, The Logic of Quanta, American Journal of Physics, 1947. Reprinted in Readings in the Philosophy of Science, Ed. H. Feigl and M. Brodbeck, Appleton-Century-Crofts, 1953. Discusses measurement, accuracy and determinism.
- J.S. Bell, On the Einstein-Poldolsky-Rosen paradox, Physics 1 195 (1964).
- A. Einstein, B. Podolsky, and N. Rosen, Can quantum-mechanical description of physical reality be considered complete? Phys. Rev. 47 777 (1935).
- G. Mackey, Mathematical Foundations of Quantum Mechanics, W. A. Benjamin, 1963 (paperback reprint by Dover 2004).
- J. von Neumann, Mathematical Foundations of Quantum Mechanics, Princeton University Press, 1955. Reprinted in paperback form. Originally published in German in 1932.
- R. Omnès, Understanding Quantum Mechanics, Princeton University Press, 1999.