A quantum-dot spin qubit with coherence limited by charge noise and fidelity higher than 99.9%

作者：Yoneda, Jun^*; Takeda, Kenta; Otsuka, Tomohiro; Nakajima, Takashi; Delbecq, Matthieu R.; Allison, Giles; Honda, Takumu; Kodera, Tetsuo; Oda, Shunri; Hoshi, Yusuke; Usami, Noritaka; Itoh, Kohei M.; Tarucha, Seigo^*

来源：Nature Nanotechnology, 2018, 13(2): 102-+.

DOI：10.1038/s41565-017-0014-x

• SINGLE-ELECTRON SPIN
• INFORMATION
• SILICON
• DEVICE

The isolation of qubits from noise sources, such as surrounding nuclear spins and spin-electric susceptibility(1-4), has enabled extensions of quantum coherence times in recent pivotal advances towards the concrete implementation of spin-based quantum computation. In fact, the possibility of achieving enhanced quantum coherence has been substantially doubted for nanostructures due to the characteristic high degree of background charge fluctuations(5-7). Still, a sizeable spin-electric coupling will be needed in realistic multiple-qubit systems to address single-spin and spin-spin manipulations(8-10). Here, we realize a single-electron spin qubit with an isotopically enriched phase coherence time (20 mu s)(11,12) and fast electrical control speed (up to 30 MHz) mediated by extrinsic spin-electric coupling. Using rapid spin rotations, we reveal that the free-evolution dephasing is caused by charge noise-rather than conventional magnetic noise-as highlighted by a 1/f spectrum extended over seven decades of frequency. The qubit exhibits superior performance with single-qubit gate fidelities exceeding 99.9% on average, offering a promising route to large-scale spin-qubit systems with fault-tolerant controllability.

• 出版日期2018-2