Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and Center for Quantum Devices, Niels Bohr Institute, 2100 Copenhagen, Denmark.
Center for Quantum Devices, Niels Bohr Institute, 2100 Copenhagen, Denmark.
Phys Rev Lett. 2014 Jan 17;112(2):026801. doi: 10.1103/PhysRevLett.112.026801. Epub 2014 Jan 14.
Multielectron spin qubits are demonstrated, and performance examined by comparing coherent exchange oscillations in coupled single-electron and multielectron quantum dots, measured in the same device. Fast (>1 GHz) exchange oscillations with a quality factor Q∼15 are found for the multielectron case, compared to Q∼2 for the single-electron case, the latter consistent with experiments in the literature. A model of dephasing that includes voltage and hyperfine noise is developed that is in good agreement with both single- and multielectron data, though in both cases additional exchange-independent dephasing is needed to obtain quantitative agreement across a broad parameter range.
多电子自旋量子位得到了展示，并通过比较在同一器件中测量的耦合单电子和多电子量子点中的相干交换振荡来检验其性能。在多电子情况下，我们发现了快（>1GHz）的交换振荡，其品质因数 Q∼15，而在单电子情况下，Q∼2，后者与文献中的实验结果一致。我们开发了一种包括电压和超精细噪声的退相模型，该模型与单电子和多电子数据都非常吻合，尽管在这两种情况下，都需要额外的与交换无关的退相来获得在广泛参数范围内的定量一致性。
