Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Nat Nanotechnol. 2016 Oct;11(10):885-889. doi: 10.1038/nnano.2016.114. Epub 2016 Jul 11.
A huge effort is underway to develop semiconductor nanostructures as low-noise qubits. A key source of dephasing for an electron spin qubit in GaAs and in naturally occurring Si is the nuclear spin bath. The electron spin is coupled to each nuclear spin by the hyperfine interaction. The same interaction also couples two remote nuclear spins via a common coupling to the delocalized electron. It has been suggested that this interaction limits both electron and nuclear spin coherence, but experimental proof is lacking. We show that the nuclear spin decoherence time decreases by two orders of magnitude on occupying an empty quantum dot with a single electron, recovering to its original value for two electrons. In the case of one electron, agreement with a model calculation verifies the hypothesis of an electron-mediated nuclear spin-nuclear spin coupling. The results establish a framework to understand the main features of this complex interaction in semiconductor nanostructures.
目前正在进行一项巨大的努力，旨在开发半导体纳米结构作为低噪声量子位。在 GaAs 和天然存在的 Si 中，电子自旋量子位的退相干的一个主要来源是核自旋浴。电子自旋通过超精细相互作用与每个核自旋耦合。相同的相互作用还通过与离域电子的公共耦合来耦合两个远程核自旋。有人认为这种相互作用限制了电子和核自旋的相干性，但缺乏实验证据。我们表明，通过占据单个电子的空量子点，核自旋退相干时间减少了两个数量级，对于两个电子则恢复到其原始值。在一个电子的情况下，与模型计算的一致性验证了电子介导的核自旋-核自旋耦合的假设。这些结果为理解半导体纳米结构中这种复杂相互作用的主要特征奠定了框架。
