Confluence of resonant laser excitation and bidirectional quantum-dot nuclear-spin polarization
Confluence of resonant laser excitation and bidirectional quantum-dot nuclear-spin polarization
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DOI：
10.1038/nphys1363
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发表时间：
2009-10-01
期刊：
影响因子：
19.6
通讯作者：
Imamoglu, A.
中科院分区：
文献类型：
--
作者：
Latta, C.;Hoegele, A.;Imamoglu, A.
共振激光散射和光子相关测量建立了量子点的类原子特性。在这里，我们表明，对于大范围的实验参数，不可能从核自旋的强烈影响中分离出基本量子点激发；磁场超过1t时的吸收谱线形状表明，核自旋极化的数量保证了量子点共振与入射激光频率的锁定。与早期的实验形成鲜明对比的是，这种核自旋极化是双向的，允许组合电子-核自旋系统动态跟踪共振两侧激光频率的变化。这一意想不到的特征源于两个自旋泵送过程之间的竞争，这两个过程试图使核自旋在相反的方向上极化。我们发现激光激发和核自旋极化的合流抑制了共振吸收的波动。一项主方程分析表明，核自旋分布会缩小，指向量子信息处理的应用。
Resonant laser scattering along with photon correlation measurements established the atom-like character of quantum dots. Here, we show that for a wide range of experimental parameters it is impossible to isolate elementary quantum-dot excitations from a strong influence of nuclear spins; the absorption lineshapes at magnetic fields exceeding 1 T indicate that the nuclear spins get polarized by an amount that ensures locking of the quantum-dot resonance to the incident laser frequency. In stark contrast to earlier experiments, this nuclear-spin polarization is bidirectional, allowing the combined electron-nuclear-spin system to track the changes in laser frequency dynamically on both sides of the resonance. This unexpected feature stems from a competition between two spin-pumping processes that attempt to polarize nuclear spins in opposite directions. We find that the confluence of laser excitation and nuclear-spin polarization suppresses the fluctuations in resonant absorption. A master-equation analysis suggests narrowing of the nuclear-spin distribution, pointing to applications in quantum information processing.