Theory of Quantum Coherence and Measurement Process
| Project/Area Number |
06640496
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
物性一般(含基礎論)
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
TAKAGI Shin Tohoku University, Dept.Physics Associate Professor, 大学院理学研究科, 助教授 (90124594)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1995: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1994: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Keywords | Coherence / Quantum Nucleation / Quantum Tunnelling / MQT / MQC / MQP / Decoherence / Quantum Measulement Process / 測定過程 / macroscopic quantam tunneling / macroscopic quantam mcleution / macroscopic quantam coherence / decoherence / 散逸 |
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| Research Abstract |
The paradox of the Schroedinger's cat will not be resolvable within the framework of quantum mechanics. A question arises whether or not quantum mechanics remains to be applicable not only to a microscopic or mesoscopic system but also to a genuine macroscopic system. With this fundamental problem in mind the following research has been carried out.
(a) The experiment under way at Tohoku University on the phase separation of a supersaturated solution of 3He in liquid 4He at temperatures below 10mK suggests that the phenomenon of macroscopic quantum nucleation (MQN) has been observed. With the aim of elucidating this phenomenon on a microscopic-theoretical foundation, we proposed a field-theoretic model which is capable of describing the quantum nucleation process. We then proceeded to deriving an effective quantum mechanics obeyed by a relevant collective degree of freedom, namely radius R of the mucleating bubble. While a preliminary result obtained from this consideration gives essentially the same potential energy governing the dynamics of the bubble as envisaged in the standard phenomenological model, it disagrees with the latter in the R-dependence of the effective inertial mass for the expanding bubble. As a consequence the phenomenological model is found to overestimate the quantum nucleation rate by a factor of 10th power of 10.
(b) In general macroscopic quantum phenomena, of which MQN is an example, can be severely affected by the very act of measuring them. It is therefore necessary to investigate the total system consisting of the macrscopic system in question and a relevant measurement apparatus. We proposed a simple model for this purpose and arrived at the following conclusion ; it is possible under certain ideal yet realizable circumstances to conduct a measurement which keeps the quantum coherence under investigation intact.
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Report
(3 results)
Research Products
(26 results)
