| Project/Area Number |
18360001
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Hokkaido University |
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Principal Investigator |
MUTO Shunichi Hokkaido University, Graduate School of Eng., Professor (00114900)
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| Co-Investigator(Kenkyū-buntansha) |
ADACHI Satoru Hokkaido University, Graduate School of Eng., Associate Professor (10221722)
TSUCHIYA Takuma Hokkaido University, Graduate School of Eng., Associate Professor (40262597)
SHIRAMINE Kenichi Hokkaido University, Graduate School of Eng., Assi. Prof. (10241358)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥14,990,000 (Direct Cost: ¥14,000,000、Indirect Cost: ¥990,000)
Fiscal Year 2007: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2006: ¥10,700,000 (Direct Cost: ¥10,700,000)
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| Keywords | nuclear spin / electron spin / quantum memory / hysteresis / quantum bit / single quantum dot / exciton / hyperfine interaction / 光配向 / 量子情報 |
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| Research Abstract |
In this project, we did a feasibility study of memory applications of quantum mechanically superposed states of an ensemble of nuclear spins. In other words, we tried to clarify the possibility of quantum information storage using quantum bit (qubit) conversion of a photon to an ensemble of nuclear spins mediated by a single electron spin through hyperfine interaction. For this purpose, we had to realize the situation where energy at the flip-flop of electron and nuclear spins is conserved, that is, the cancellation of external magnetic field and the effective nuclear field.
In 2006, we studied the formation of nuclear field as functions of intensity and degree of circular polarization of excitation light on a single InAlAs/GaAs quantum dot (QD). As a result, we observed hysteresis in the nuclear magnetic field as a function of intensity of the excitation light which is circularly polarized. We can interpret this phenomenon as a nuclear spin switching and we concluded that the cancellation of external magnetic field and the effective nuclear field was realized. This is a condition necessary for the electron nuclear spin qubit conversion.
In 2007, we advanced our study to include the magnetic field dependence. Upon increasing field the nuclear field increased to a certain threshold value above which the nuclear field discontinuously decreased. Comparison with theoretical calculations tells us that the nuclear field completely cancelled the external magnetic field. Unfortunately, however, this nuclear field is determined by the balance of the formation and destruction of nuclear spin polarization, and is not indicating the perfect polarization or the nuclear dark state both of which can be used for the electron nuclear spin qubit conversion. This shows that the current status of InAlAs QD is not suitable for the qubit conversion and either enhancement of nuclear spin formation or reduction of spin deformation is needed.
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