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:''This article is intended for those already familiar with quantum mechanics and its attendant interpretational difficulties. Readers who are new to the subject may first want to read the introduction to quantum mechanics.'' Relational quantum mechanics (RQM) is an interpretation of quantum mechanics which treats the state of a quantum system as being observer-dependent, that is, the state ''is'' the relation between the observer and the system. This interpretation was first delineated by Carlo Rovelli in a 1994 preprint, and has since been expanded upon by a number of theorists. It is inspired by the key idea behind Special Relativity, that the details of an observation depend on the reference frame of the observer, and uses some ideas from Wheeler on quantum information.〔Wheeler (1990): pg. 3〕 The physical content of the theory is not to do with objects themselves, but the relations between them. As Rovelli puts it: "''Quantum mechanics is a theory about the physical description of physical systems relative to other systems, and this is a complete description of the world''".〔Rovelli, C. (1996), "Relational quantum mechanics", ''International Journal of Theoretical Physics'', 35: 1637-1678.〕 The essential idea behind RQM is that different observers may give different accounts of the same series of events: for example, to one observer at a given point in time, a system may be in a single, "collapsed" eigenstate, while to another observer at the same time, it may appear to be in a superposition of two or more states. Consequently, if quantum mechanics is to be a complete theory, RQM argues that the notion of "state" describes not the observed system itself, but the relationship, or correlation, between the system and its observer(s). The state vector of conventional quantum mechanics becomes a description of the correlation of some ''degrees of freedom'' in the observer, with respect to the observed system. However, it is held by RQM that this applies to all physical objects, whether or not they are conscious or macroscopic (all systems are quantum systems). Any "measurement event" is seen simply as an ordinary physical interaction, an establishment of the sort of correlation discussed above. The proponents of the relational interpretation argue that the approach clears up a number of traditional interpretational difficulties with quantum mechanics, while being simultaneously conceptually elegant and ontologically parsimonious. ==History and development== Relational quantum mechanics arose from a historical comparison of the quandaries posed by the interpretation of quantum mechanics with the situation after the Lorentz transformations were formulated but before special relativity. Rovelli felt that just as there was an "incorrect assumption" underlying the pre-relativistic interpretation of Lorentz's equations, which was corrected by Einstein's deriving them from Lorentz covariance and the constancy of the speed of light in all reference frames, so a similarly incorrect assumption underlies many attempts to make sense of the quantum formalism, which was responsible for many of the interpretational difficulties posed by the theory. This incorrect assumption, he said, was that of an observer-independent state of a system, and he laid out the foundations of this interpretation to try to overcome the difficulty.〔Rovelli (1996): pg. 2〕 The idea has been expanded upon by Lee Smolin〔Smolin (1995)〕 and Louis Crane,〔Crane (1993)〕 who have both applied the concept to quantum cosmology, and the interpretation has been applied to the EPR paradox, revealing not only a peaceful co-existence between quantum mechanics and special relativity, but a formal indication of a completely local character to reality.〔Laudisa (2001)〕〔Rovelli & Smerlak (2006)〕 David Mermin has contributed to the relational approach in his "Ithaca interpretation."〔Mermin, N.D. (1996, 1998).〕 He describes "correlations without correlata", meaning that relations have more concrete existence than the objects being related. The name "Zero Worlds" has also been popularized by Garret.〔Garret, R. (Jan 2011) "The Quantum Conspiracy: What Popularizers Of QM Don't Want You To Know" ((slides ), (video )).〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Relational quantum mechanics」の詳細全文を読む スポンサード リンク
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