Nat Mater. 2011 Aug 28;10(11):844-8. doi: 10.1038/nmat3102.
Highly polarized nuclear spins within a semiconductor quantum dot induce effective magnetic (Overhauser) fields of up to several Tesla acting on the electron spin, or up to a few hundred mT for the hole spin. Recently this has been recognized as a resource for intrinsic control of quantum-dot-based spin quantum bits. However, only static long-lived Overhauser fields could be used. Here we demonstrate fast redirection on the microsecond timescale of Overhauser fields on the order of 0.5 T experienced by a single electron spin in an optically pumped GaAs quantum dot. This has been achieved using coherent control of an ensemble of 10(5) optically polarized nuclear spins by sequences of short radiofrequency pulses. These results open the way to a new class of experiments using radiofrequency techniques to achieve highly correlated nuclear spins in quantum dots, such as adiabatic demagnetization in the rotating frame leading to sub-μK nuclear spin temperatures, rapid adiabatic passage, and spin squeezing.
半导体量子点中高度极化的核自旋会产生高达数特斯拉的有效磁场（奥弗豪瑟场），作用于电子自旋，或高达数百毫特斯拉作用于空穴自旋。最近，人们已经认识到这是一种用于内在控制基于量子点的自旋量子位的资源。然而，只能使用静态的、长寿命的奥弗豪瑟场。在这里，我们演示了在微秒时间尺度内对单个电子自旋在光泵浦 GaAs 量子点中经历的约 0.5 T 的奥弗豪瑟场的快速重定向。这是通过使用短射频脉冲序列对 10^5 个光学极化核自旋的集体进行相干控制来实现的。这些结果为使用射频技术在量子点中实现高度相关的核自旋开辟了新的实验途径，例如在旋转框架中进行绝热去磁，导致核自旋温度降至亚微开尔文、快速绝热通道和自旋压缩。
