Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA.
Nat Nanotechnol. 2011 Feb;6(2):112-5. doi: 10.1038/nnano.2010.252. Epub 2010 Dec 19.
Progress in the synthesis of colloidal quantum dots has recently provided access to entirely new forms of diluted magnetic semiconductors, some of which may find use in quantum computation. The usefulness of a spin qubit is defined by its Rabi frequency, which determines the operation time, and its coherence time, which sets the error correction window. However, the spin dynamics of magnetic impurity ions in colloidal doped quantum dots remain entirely unexplored. Here, we use pulsed electron paramagnetic resonance spectroscopy to demonstrate long spin coherence times of ∼0.9 µs in colloidal ZnO quantum dots containing the paramagnetic dopant Mn(2+), as well as Rabi oscillations with frequencies ranging between 2 and 20 MHz depending on microwave power. We also observe electron spin echo envelope modulations of the Mn(2+) signal due to hyperfine coupling with protons outside the quantum dots, a situation unique to the colloidal form of quantum dots, and not observed to date.
最近，胶体量子点合成方面的进展为完全新型的稀磁半导体的制备提供了可能，其中一些半导体可能在量子计算中得到应用。一个自旋量子比特的有用性取决于它的拉比频率，拉比频率决定了操作时间，还取决于它的相干时间，相干时间决定了纠错窗口。然而，胶体掺杂量子点中磁性杂质离子的自旋动力学仍然完全没有得到探索。在这里，我们使用脉冲电子顺磁共振波谱技术，在含有顺磁掺杂剂 Mn(2+)的胶体 ZnO 量子点中证明了长达约 0.9 µs 的长自旋相干时间，并且 Rabi 振荡频率范围在 2 到 20 MHz 之间，这取决于微波功率。我们还观察到 Mn(2+)信号的电子自旋回波包络调制，这是由于与量子点外的质子的超精细耦合，这种情况是胶体量子点特有的，迄今为止尚未观察到。
