Qubits based on merons in magnetic nanodisks
Jing Xia, Xichao Zhang, Xiaoxi Liu, Yan Zhou, Motohiko Ezawa
Abstract
Abstract A meron is a classical topological soliton having a half topological charge. It could be materialized in a magnetic disk. However, it will become a quantum mechanical object when its size is of the order of nanometers. Here, we propose to use a nanoscale meron in a magnetic nanodisk as a qubit, where the up and down directions of the core spin are assigned to be the qubit states $$\left\vert 0\right\rangle$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mfenced> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> </mml:mfenced> </mml:math> and $$\left\vert 1\right\rangle$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mfenced> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:mfenced> </mml:math> . We first numerically show that a meron with the radius containing as small as 7 spins can be stabilized in a ferromagnetic nanodisk classically. Then, we show theoretically that universal quantum computation is possible based on merons by explicitly constructing the arbitrary phase-shift gate, Hadamard gate, and CNOT gate. They are executed by applying a magnetic field or spin-polarized current. Our results may be useful for the implementation of quantum computation based on topological spin textures in nanomagnets.