Cywiński Lukasz, Witzel Wayne M, Das Sarma S
Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
Phys Rev Lett. 2009 Feb 6;102(5):057601. doi: 10.1103/PhysRevLett.102.057601. Epub 2009 Feb 3.
We investigate pure dephasing decoherence (free induction decay and spin echo) of a spin qubit interacting with a nuclear spin bath. While for infinite magnetic field B the only decoherence mechanism is spectral diffusion due to dipolar flip-flops of nuclear spins, with decreasing B the hyperfine-mediated interactions between the nuclear spins become important. We give a theory of decoherence due to these interactions which takes advantage of their long-range nature. For a thermal uncorrelated bath we show that our theory is applicable down to B approximately 10 mT, allowing for comparison with recent experiments in GaAs quantum dots.
我们研究了与核自旋库相互作用的自旋量子比特的纯退相退相干（自由感应衰减和自旋回波）。对于无限大的磁场B，唯一的退相干机制是由于核自旋的偶极翻转引起的谱扩散，随着B的减小，核自旋之间的超精细介导相互作用变得重要。我们给出了由于这些相互作用导致的退相干理论，该理论利用了它们的长程性质。对于热不相关库，我们表明我们的理论适用于低至约10 mT的B，从而可以与最近在砷化镓量子点中的实验进行比较。
