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 500 MHz to close-to-off and perform a conditional spin-flip in 24 ns. 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.

半导体自旋量子位提供了利用工业晶体管技术生产大规模量子计算机的潜力。硅孔自旋量子位受益于快速全电量子位控制和抵消电荷和核自旋噪声的最佳点。然而，两个量子位相互作用的演示仍然是一个开放的挑战。一个缺失的因素是对存在强自旋轨道相互作用的交换耦合的理解。在这里，我们研究了硅鳍场效应晶体管中的两个空穴自旋量子位，硅鳍场效应晶体管是当今半导体行业的主力器件。我们展示了交换分裂从 500 MHz 以上到接近关闭的电可调性，并在 24 ns 内执行条件自旋翻转。由于自旋轨道相互作用，交换是各向异性的。从一个量子点隧道到另一个量子点时，自旋旋转了近 180 度。交换哈密顿量不再具有海森堡形式，并且可以进行设计，使其能够实现两个量子位控制的旋转门，而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，使得该概念对于量子位之间的变化具有鲁棒性，表明它是实现大规模量子计算机的合适方法。