2004 Fiscal Year Final Research Report Summary
Exciton Rabi oscillation in GaAs quantum dots
| Project/Area Number |
15340093
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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 |
Condensed matter physics I
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
MINAMI Fujio Tokyo Institute of Technology, Department of Physics, Professor, 大学院・理工学研究科, 教授 (30200083)
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| Project Period (FY) |
2003 – 2004
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| Keywords | photon echo / Rabi oscillation / quantum dot / exciton / GaAs / dephasing |
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| Research Abstract |
We performed the photon echo experiment on GaAs quantum dots at 5K. The excitation light source was a fs Ti-Sapphire laser. The excitation photon energy was tuned to cover the lowest exciton in GaAs quantum dots. A dominant signal is observed at the zero time delay, which is due to photon echoes from the GaAs substrate and is unrelated to the quantum dots. For longer delays, we can observe a slowly decaying signal with a time constant of 〜1 ns. This signal is due to the dephasing of the exciton coherence in the quantum dots. Therefore, it can be concluded that the dephasing time of the exciton is extremely long (〜1 ns) in the quantum dots as compared to that in usual quantum wells (〜1ps).
When changing the exciting pulse power, the signal intensity of the photon echo varys greatly. The echo intensity is found to oscilate as the excitation power increases. It can be understood that this oscillation is analogous to the Rabi oscillation, which is observed in resonantly driven two level systems. It is therefore considered that we observed the Rabi oscillation of the exciton in the quantum dots. It is noted that the Rabi oscillation can be observed under relatively low excitation power. Because the Rabi oscillation is an essential phenomenon to rotate q-bit, this result shows that the semiconductor quantum dots are promising as the logical circuit material of the quantum computing.
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