2005 Fiscal Year Final Research Report Summary
Time development of quantum systems and field theory
| Project/Area Number |
14540280
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | Waseda University |
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Principal Investigator |
NAKAZATO Hiromichi Waseda University, Faculty of Science and Engineering, Professor, 理工学術院, 教授 (00180266)
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| Co-Investigator(Kenkyū-buntansha) |
YUASA Kazuya Waseda University, Faculty of Science and Engineering, Research Assistant, 理工学術院, 助手 (90339721)
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| Project Period (FY) |
2002 – 2005
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| Keywords | time evolution of quantum systems / purification of quantum states / suppression of de coherence / Lindblad-type master equation |
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| Research Abstract |
In this research project, the temporal evolution of quantum systems, especially that under the influence of the action of quantum measurements, has mainly been investigated.
As is well known, the temporal behavior of a quantum system is classified into three characteristic stages, i.e., the quadratic (Gaussian) behavior at short times, the exponential decay at intermediate times and the power decay at long times and on the basis of a solvable model, we first demonstrated these characteristics analytically.
Next, we have proposed a new scheme of driving a quantum system under investigation to a pure state irrespectively of its initial (in general mixed) state, by means of repeated measurements of another quantum system in interaction with the former. A remarkable feature of this method is that the two important notions in this kind of research work, that is, the fidelity and the yield, can be made compatible, the condition which is not easily implemented in many other attempts. Moreover, since its fundamental idea is so simple and general, it retains high flexibility and applicability and in fact, it has been generalized and applied to many different physical situations. Among such applications, purification of qubit systems, extraction of entangled states that can be spatially separated, construction of filters for more general quantum states with the help of dynamical quantum Zeno effects and an experimental proposal of this scheme in the quantum dot system are noted.
We have also investigated the master equation that usually describes a quantum system under the influence of its dissipative and decohering environment to clarify its mathematically subtle points so far somehow overlooked.
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Research Products
(25 results)
