Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK.
EPSRC National Centre for III-V Technologies, University of Sheffield, Sheffield, S1 3JD, UK.
Nat Commun. 2016 Sep 12;7:12745. doi: 10.1038/ncomms12745.
The interaction between a confined electron and the nuclei of an optically active quantum dot provides a uniquely rich manifestation of the central spin problem. Coherent qubit control combines with an ultrafast spin-photon interface to make these confined spins attractive candidates for quantum optical networks. Reaching the full potential of spin coherence has been hindered by the lack of knowledge of the key irreversible environment dynamics. Through all-optical Hahn echo decoupling we now recover the intrinsic coherence time set by the interaction with the inhomogeneously strained nuclear bath. The high-frequency nuclear dynamics are directly imprinted on the electron spin coherence, resulting in a dramatic jump of coherence times from few tens of nanoseconds to the microsecond regime between 2 and 3 T magnetic field and an exponential decay of coherence at high fields. These results reveal spin coherence can be improved by applying large magnetic fields and reducing strain inhomogeneity.
受限电子与光学活性量子点的原子核之间的相互作用为中央自旋问题提供了独特而丰富的表现形式。相干量子比特控制与超快自旋-光子接口相结合，使这些受限自旋成为量子光学网络的有吸引力的候选者。自旋相干性的充分发挥受到对关键不可逆环境动力学缺乏了解的阻碍。通过全光哈恩回波去耦，我们现在恢复了由与非均匀应变核浴相互作用设定的固有相干时间。高频核动力学直接印刻在电子自旋相干性上，导致在 2 到 3 特斯拉磁场之间，相干时间从几十纳秒急剧跃升至微秒范围，并在高场下呈指数衰减。这些结果表明，通过施加强磁场和减少应变不均匀性，可以提高自旋相干性。
