Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Sydney, Sydney, New South Wales, Australia.
Center for Computing Research, Sandia National Laboratories, Albuquerque, NM, USA.
Nature. 2020 Mar;579(7798):205-209. doi: 10.1038/s41586-020-2057-7. Epub 2020 Mar 11.
Nuclear spins are highly coherent quantum objects. In large ensembles, their control and detection via magnetic resonance is widely exploited, for example, in chemistry, medicine, materials science and mining. Nuclear spins also featured in early proposals for solid-state quantum computers and demonstrations of quantum search and factoring algorithms. Scaling up such concepts requires controlling individual nuclei, which can be detected when coupled to an electron. However, the need to address the nuclei via oscillating magnetic fields complicates their integration in multi-spin nanoscale devices, because the field cannot be localized or screened. Control via electric fields would resolve this problem, but previous methods relied on transducing electric signals into magnetic fields via the electron-nuclear hyperfine interaction, which severely affects nuclear coherence. Here we demonstrate the coherent quantum control of a single Sb (spin-7/2) nucleus using localized electric fields produced within a silicon nanoelectronic device. The method exploits an idea proposed in 1961 but not previously realized experimentally with a single nucleus. Our results are quantitatively supported by a microscopic theoretical model that reveals how the purely electrical modulation of the nuclear electric quadrupole interaction results in coherent nuclear spin transitions that are uniquely addressable owing to lattice strain. The spin dephasing time, 0.1 seconds, is orders of magnitude longer than those obtained by methods that require a coupled electron spin to achieve electrical driving. These results show that high-spin quadrupolar nuclei could be deployed as chaotic models, strain sensors and hybrid spin-mechanical quantum systems using all-electrical controls. Integrating electrically controllable nuclei with quantum dots could pave the way to scalable, nuclear- and electron-spin-based quantum computers in silicon that operate without the need for oscillating magnetic fields.
核自旋是高度相干的量子物体。在大规模体系中，通过磁共振对其进行控制和检测被广泛应用于化学、医学、材料科学和矿业等领域。核自旋也出现在早期的固态量子计算机方案和量子搜索和因式分解算法的演示中。要扩展这些概念，需要控制单个核，当它们与电子耦合时可以检测到。然而，需要通过振荡磁场来寻址核，这使得它们在多自旋纳米尺度器件中的集成变得复杂，因为磁场无法被局部化或屏蔽。通过电场进行控制可以解决这个问题，但以前的方法依赖于通过电子-核超精细相互作用将电信号转换为磁场，这严重影响了核的相干性。在这里，我们展示了使用硅纳米电子器件内产生的局部电场对单个 Sb（自旋为 7/2）核进行相干量子控制。该方法利用了 1961 年提出的一个想法，但以前没有用单个核实验实现过。我们的结果得到了微观理论模型的定量支持，该模型揭示了如何通过核电四极相互作用的纯电场调制导致相干核自旋跃迁，由于晶格应变，这些跃迁是唯一可寻址的。自旋退相时间为 0.1 秒，比需要耦合电子自旋来实现电驱动的方法长几个数量级。这些结果表明，高自旋四极核可以作为混沌模型、应变传感器和基于混合自旋-机械的量子系统来使用，这些系统都可以通过全电控制来实现。将电可控核与量子点集成，可能为基于硅的可扩展、核和电子自旋量子计算机铺平道路，这些计算机无需振荡磁场即可运行。
