2016 Fiscal Year Research-status Report
Spin hot spots in semiconductor quantum dots
| Project/Area Number |
16K05411
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
STANO PETER 国立研究開発法人理化学研究所, 創発物性科学研究センター, 上級研究員 (10722746)
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | スピン物性（半導体） / spin-orbit coupling / decoherence / quantum dot / spin qubit |
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| Outline of Annual Research Achievements |
We theoretically investigated the influence of the orientation of the magnetic field and a quantum dot on the quality of an electrically controlled qubit realized in a gated semiconductor quantum dot. We found that, due to the anisotropy of the spin-orbit interactions, by varying the two orientations it is possible to tune the qubit in the sense of optimizing the ratio of its couplings to phonons and to a control electric field. Second, in collaboration with experimentalists, we were able to separate the effects of nuclear spins and spin-orbit interactions on the spin-flip events observed in real time in the electron tunneling in a weakly coupled two-electron double quantum dot in GaAs.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
The two results that we achieved in the first year are among the key goals of the project. Namely, by developing an elastic transition theory, we demonstrated how to extract the strengths of spin-orbit interactions from a Pauli Spin Blockade measurement. Second, we specified conditions under which an optimal quantum dot setup can be reached by solely reorienting the magnetic field, and when a specific positioning of the dot is required. Here we found that the knowledge of the relative sign of the spin-orbit interaction strengths is needed to select optimal dot geometry. We predict that the best performing qubits are such where the quantum dot main axis is along [110] with respect to the crystallographic directions. The project goals concerning GaAs material are thus finished.
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| Strategy for Future Research Activity |
In the next year I will focus on two tasks. The first is to establish theoretically how the quantum dot orientation can be determined for dots which are not intentionally anisotropic (that is, the gates which form them are approximately rotationaly symmetric). This is necessary for measurement of the spin-orbit constants using, for example, single dots. Second, after successful determination of the spin-orbit lengths in GaAs, I will try to apply the knowledge and methods to Silicon. Here not only strengths, but also form of these interactions are unclear. I will try to elucidate this question.
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| Causes of Carryover |
In the next fiscal year, I plan to use the financial support mostly for travel. I plan to attend several international conferences where I will present results obtained in this project.
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| Expenditure Plan for Carryover Budget |
I plan to use 600 000 Yen for conferences and 200 000 Yen as other costs. The other cost will be used to cover expenses for books, physics society memberships, software licences and similar.
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