Aldeghi Michele, Allenspach Rolf, Vervelaki Andriani, Jetter Daniel, Bagani Kousik, Braakman Floris, Poggio Martino, Salis Gian
IBM Research─Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland.
Department of Physics, University of Basel, 4056 Basel, Switzerland.
Nano Lett. 2025 Feb 5;25(5):1838-1844. doi: 10.1021/acs.nanolett.4c05037. Epub 2025 Jan 22.
The inhomogeneous magnetic stray field of micromagnets has been extensively used to manipulate electron spin qubits. By means of micromagnetic simulations and scanning superconducting quantum interference device microscopy, we show that the polycrystallinity of the magnet and nonuniform magnetization significantly impact the stray field and corresponding qubit properties. The random orientation of the crystal axis in polycrystalline Co magnets alters the qubit frequencies by up to 0.5 GHz, compromising single qubit addressability and single gate fidelities. We map the stray field of Fe micromagnets with an applied magnetic field of up to 500 mT, finding field gradients above 1 mT/nm. The measured gradients and the lower magnetocrystalline anisotropy of Fe demonstrate the advantage of using Fe instead of Co as magnets in spin qubit devices. These properties of Fe also enabled us to design a 2D arrangement of nanomagnets for driving spin qubits distributed on a 2D lattice.
微磁体的非均匀杂散磁场已被广泛用于操纵电子自旋量子比特。通过微磁模拟和扫描超导量子干涉装置显微镜，我们表明磁体的多晶性和不均匀磁化会显著影响杂散磁场和相应的量子比特特性。多晶钴磁体中晶轴的随机取向会使量子比特频率改变高达0.5 GHz，从而影响单量子比特可寻址性和单门保真度。我们绘制了施加高达500 mT磁场时铁微磁体的杂散磁场，发现场梯度高于1 mT/nm。测量得到的梯度以及铁较低的磁晶各向异性表明，在自旋量子比特器件中使用铁而非钴作为磁体具有优势。铁的这些特性还使我们能够设计一种纳米磁体的二维排列，用于驱动分布在二维晶格上的自旋量子比特。
