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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.'' The relational approach to quantum physics is an alternative approach to and interpretation of quantum mechanics. It asserts that the physical world can only be studied accurately in terms of ''relationships'' between systems, as all experimentally verifiable facts about the world result explicitly from interactions (such as the interaction between a light field and a detector). According to the relational approach, the assumption that objects possess absolute properties (such as an absolute particle, independent of any detection frame) inevitably leads to ambiguities and paradoxes when these objects are studied closely. The approach was adopted, in a time span of 1992-1996, by Q. Zheng, S. Hughes, and T. Kobayashi in the University of Tokyo.〔( Zheng ''et al.'' (1992, 1996) )〕 As early as in 1985, S. Kochen suggested that the paradoxes of quantum physics could be overcome by developing a relational approach, which was needed at one time to solve the paradoxes of relativistic physics of space and time.〔S. Kochen, Symposium of the Foundations of Modern Physics: 50 Years of the Einstein-Podolsky-Rosen Gedankenexperiment, (World Scientific Publishing Co., Singapore, 1985), pp. 151-69.〕〔For later work, see (John Conway and Simon Kochen ) ''The Free Will Theorem''.〕 It is also hoped that this entry will serve as a complement to Rovelli’s relational quantum mechanics (RQM). Historically, the theory of relativity and quantum mechanics were intertwined with each other and the compatibility between both theories was a main theme throughout the Bohr-Einstein debate.〔M. Jammer, The Philosophy of Quantum Mechanics, (Wiley, New York, 1974), p. 109.〕 In both theories the physicists emphasized that only measurable quantities, that is, observables, belong in a theory. Bohr compared his approach to Einstein’s theory of relativity and asserted that in the treatment of quantum processes the complementarity of the measuring results cannot be ignored, just as in high-speed phenomena the relativity of observation cannot be neglected when the simultaneity comes into question. But Einstein replied: “A good joke should not be repeated too often.” 〔P. Frank, Einstein-His Life and Times, (Knopf, New York, 1947), p. 216.〕 The debate continued in connection with Einstein-Podolsky-Rosen (EPR) paradox, and Bohr proposed the relational conception of quantum states.〔M. Jammer, The Philosophy of Quantum Mechanics, (Wiley, New York, 1974), p. 197.〕 Through their analysis Bohm and Schumacher concluded that the characteristic feature of this debate is the failure to communicate due to the absence of a full harmony of quantum mechanics with relativity.〔D. Bohm and D. L. Schumacher, On the failure of communication between Bohr and Einstein, (Preprint, 1972). 〕 Modern attempts to embrace a relational approach with interpretations of quantum mechanics have been tried many times, ranging from Everett's relative-state interpretation (Everett, 1957), sigma algebra of interactive properties (Kochen, 1979), quantum reference systems (Bene, 1992), quantum theory of the universe (Smolin, 1995), to relational quantum mechanics (Rovelli, 1996). They more or less emphasize the relational nature of quantum states. For more information, please refer to the further reading list. ==Background== As is well known, Einstein's theory of relativity, which involves a profound analysis of time and space, introduced radical changes, not only in our basic concepts, but also in our modes of physical reasoning. The essence of Einstein's theory was to adopt a relational approach to the notions of time and space,〔D. Bohm, The Special Theory of Relativity (Benjamin, New York, 1965).〕 which mathematically can be expressed through the Lorentz space-time transformations. Although the mathematical structure of the Lorentz ether theory, which leaves the speed of light ''in vacuo'', ''c'', a universal constant, is equivalent to that of Einstein's, there is nevertheless a drastic difference in the way to conceive it. On the one hand, Lorentz began with retaining the customary concepts of absolute time and space of the older Newtonian mechanics, and by considering changes in the observing instruments. The invariant nature of ''c'', as measured experimentally from the Michelson-Morley experiment, was successfully explained by the so-called 'Lorentz contraction', moving through the hypothetical ether. However, this theory led to the difficulty that the exact values of the 'true' distances and times, with respect to a detection scheme at rest in the ether, became somewhat ambiguous and unknowable. Einstein, on the other hand, by commencing with the observed facts, regarded time and space a ''priori'' as a certain class of 'coordinates' merely expressing ''relationships'' of an event to the measuring instruments. On the basis of a constant speed of light, both time and space become ''relative'' concepts, fundamentally dependent of the observer. The developments of quantum formulation early this century has also led physicists to question the Newtonian concepts of physical objects, such as 'particle' and 'wave', which are basic ideas in all of classical physics. Subsequently, Heisenberg in his pioneering paper 〔W. Heisenberg, Z. Phys. 43, 172 (1927). For an English translation, see Quantum Theory and Measurement ed. J. A. Wheeler and W. H. Zurek (Princeton Univ. Press, New Jersey, 1983), pp. 62-84.〕 developed a conceptual framework that in a way retained all the classical concepts, and plays a great role in the Copenhagen interpretation. This basic new step was to study the disturbance of observing instruments, and for this purpose, Heisenberg constructed the famous ''gedanken'' microscope experiment to measure very accurately the position of an electron. It was found that since the individual quanta of action must be taken into account in the measurement process, the irreducible disturbance rendered it impossible to assign ''simultaneously'' the precise values of position and momentum. Consequently, by considering the uncontrollable influence from the observation itself, the notion of particle into quantum mechanics was preserved, and the uncertainty principle was born. 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 approach to quantum physics」の詳細全文を読む スポンサード リンク
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