Optically controlled locking of the nuclear field via coherent dark-state spectroscopy
Optically controlled locking of the nuclear field via coherent dark-state spectroscopy
复制标题
DOI：
10.1038/nature08120
复制
发表时间：
2009-06
期刊：
影响因子：
64.8
通讯作者：
Bosong Sun;Xiaodong Xu;W. Yao;D. Steel;A. Bracker;D. Gammon;L. Sham
中科院分区：
文献类型：
--
作者：
Bosong Sun;Xiaodong Xu;W. Yao;D. Steel;A. Bracker;D. Gammon;L. Sham
半导体量子点内捕获的单个电子或空穴自旋形成了许多拟议的量子逻辑器件的基础。在III-V族材料中，单自旋的两个基态之间的共振和相干性不可避免地受到晶格核自旋通过超精细相互作用的影响，而单自旋的动力学也影响核环境，。最近的努力，已经取得了通过抑制核自旋涨落来保护量子点中自旋的相干性。然而，在一个点中的一个自旋的相干控制与同时抑制的核波动尚未实现。在这里，我们报告的抑制核场波动的单电荷量子点远低于热值，如所示的增强的单电子自旋退相时间T2 *，我们使用相干暗态光谱测量。发现核涨落的抑制是由于空穴自旋辅助的动态核自旋极化反馈过程，其中核场的稳定值仅由固定激光功率下的激光频率决定。这种核场锁定在三激光测量中得到进一步证明，表明电子自旋T2 * 可能增强几百倍。这是一种简单而有效的方法，可以在不使用“自旋回波”技术的情况下提高电子自旋相干时间。我们希望我们的研究结果将使核自旋环境的重复性制备的控制和测量的一个单一的自旋与最小的统计增宽。
A single electron or hole spin trapped inside a semiconductor quantum dot forms the foundation for many proposed quantum logic devices,,,,,. In group III–V materials, the resonance and coherence between two ground states of the single spin are inevitably affected by the lattice nuclear spins through the hyperfine interaction,,, while the dynamics of the single spin also influence the nuclear environment,,,,,. Recent efforts,have been made to protect the coherence of spins in quantum dots by suppressing the nuclear spin fluctuations. However, coherent control of a single spin in a single dot with simultaneous suppression of the nuclear fluctuations has yet to be achieved. Here we report the suppression of nuclear field fluctuations in a singly charged quantum dot to well below the thermal value, as shown by an enhancement of the single electron spin dephasing timeT2*, which we measure using coherent dark-state spectroscopy. The suppression of nuclear fluctuations is found to result from a hole-spin assisted dynamic nuclear spin polarization feedback process, where the stable value of the nuclear field is determined only by the laser frequencies at fixed laser powers. This nuclear field locking is further demonstrated in a three-laser measurement, indicating a possible enhancement of the electron spinT2* by a factor of several hundred. This is a simple and powerful method of enhancing the electron spin coherence time without use of ‘spin echo’-type techniques,. We expect that our results will enable the reproducible preparation of the nuclear spin environment for repetitive control and measurement of a single spin with minimal statistical broadening.