近日，瑞士巴塞尔大学的Andreas V. Kuhlmann&Dominik M. Zumbühl&Simon Geyer及其研究团队取得一项新进展。经过不懈努力，他们揭示两个空穴自旋量子比特的各向异性交换相互作用。相关研究成果已于2024年5月6日在国际知名学术期刊《自然—物理学》上发表。
该研究团队研究了硅鳍场效应晶体管中的两个空穴自旋量子比特，硅鳍场效应晶体管是当今半导体工业的主力器件。研究人员展示了交换分裂的电气可调性，该性能可从500MHz以上调整至接近关闭状态，并在短短24纳秒内实现了条件自旋翻转。由于自旋轨道相互作用的影响，交换过程表现出各向异性，当自旋从一个量子点隧穿至另一个时，几乎完成了180度的旋转。
这一研究中，交换哈密顿量不再遵循传统的海森堡形式，但可以特别设计以实现双量子比特控制的旋转门，无需在速度和保真度之间进行权衡。这种理想的行为适用于广泛的磁场方向，展现了量子比特间变化的鲁棒性，为实现大规模量子计算机提供了一种合适方法。
据悉，半导体自旋量子比特展现了利用工业晶体管技术制造大规模量子计算机的巨大潜力。硅空穴自旋量子比特因其快速的全电量子比特控制和独特的“甜点”特性，能有效抵消电荷和核自旋噪声的影响。然而，展示双量子比特之间的相互作用仍是一个待解难题。其中一个关键挑战在于理解强自旋轨道相互作用下的交换耦合机制。
附：英文原文
Title: Anisotropic exchange interaction of two hole-spin qubits
Author: Geyer, Simon, Hetnyi, Bence, Bosco, Stefano, Camenzind, Leon C., Eggli, Rafael S., Fuhrer, Andreas, Loss, Daniel, Warburton, Richard J., Zumbhl, Dominik M., Kuhlmann, Andreas V.
Issue&Volume: 2024-05-06
Abstract: Semiconductor spin qubits offer the potential to employ industrial transistor technology to produce large-scale quantum computers. Silicon hole spin qubits benefit from fast all-electrical qubit control and sweet spots to counteract charge and nuclear spin noise. However, the demonstration of a two-qubit interaction has remained an open challenge. One missing factor is an understanding of the exchange coupling in the presence of a strong spin–orbit interaction. Here we study two hole-spin qubits in a silicon fin field-effect transistor, the workhorse device of today’s semiconductor industry. We demonstrate electrical tunability of the exchange splitting from above 500MHz to close-to-off and perform a conditional spin-flip in 24ns. The exchange is anisotropic because of the spin–orbit interaction. Upon tunnelling from one quantum dot to the other, the spin is rotated by almost 180 degrees. The exchange Hamiltonian no longer has the Heisenberg form and can be engineered such that it enables two-qubit controlled rotation gates without a trade-off between speed and fidelity. This ideal behaviour applies over a wide range of magnetic field orientations, rendering the concept robust with respect to variations from qubit to qubit, indicating that it is a suitable approach for realizing a large-scale quantum computer.
DOI: 10.1038/s41567-024-02481-5
Source: https://www.nature.com/articles/s41567-024-02481-5