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Exciton Rabi oscillation in GaAs quantum dots

GaAs 量子点中的激子拉比振荡

基本信息

批准号：
15340093
负责人：
MINAMI Fujio
金额：
$ 10.69万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15340093/
关键词：
photon echo Rabi oscillation quantum dot exciton GaAs dephasing 非マルコフ過程

项目摘要

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.

我们在 5K 下对 GaAs 量子点进行了光子回波实验。激发光源是飞秒钛蓝宝石激光器。调整激发光子能量以覆盖 GaAs 量子点中的最低激子。在零时间延迟处观察到主要信号，这是由于来自 GaAs 衬底的光子回波造成的，与量子点无关。对于较长的延迟，我们可以观察到时间常数为〜1 ns 的缓慢衰减信号。该信号是由于量子点中激子相干性的移相造成的。因此，可以得出结论，与普通量子阱中的激子相移时间（〜1ps）相比，量子点中激子的相相时间极长（〜1ns）。当改变激发脉冲功率时，光子回波的信号强度变化很大。发现回波强度随着激励功率的增加而振荡。可以理解，这种振荡类似于在谐振驱动的两能级系统中观察到的拉比振荡。因此，认为我们观察到了量子点中激子的拉比振荡。值得注意的是，在相对较低的激励功率下可以观察到拉比振荡。由于拉比振荡是旋转q位的基本现象，这一结果表明半导体量子点有望作为量子计算的逻辑电路材料。