Micromagnets for novel qubits for quantum computation*

One of the challenges in realizing scalable quantum computing is designing hardware that can store and manipulate quantum information at high rates. Superconducting qubits have a number of advantages, but their operational temperature is tens of mK[1]. In this work, we investigate an alternative platform for solid-state qubits based on magnons. The proposed magnetic qubit stores quantum information in the Kittel mode, which is a uniform magnon mode. The anharmonicity required to energetically isolate the qubit states is obtained through a magnetic anisotropy[2], which depends strongly on the boundary conditions (shape), strain and crystalline symmetries. The magnitude of these anisotropies can be quite large, allowing for a highly tunable system. We present calculations of the magnon spectrum in the presence of various forms of anisotropy, and analyze the dependence of non-linear magnon spectrum on the anisotropy strength. In particular, we apply our calculations to  Yttrium Iron Garnet[3] and Barium Ferrite[4]  materials.

1.P. Krantz, M. Kjaergaard, F. Yan, T. P. Orlando, S. Gustavsson, W. D. Oliver. Appl. Phys. Rev.1 June 2019; 6(2).

2.D. Stancil, A. Prabhakar. Spin Waves theory and Applications.

3.Vladimir Cherepanov, Igor Kolokolov, Victor L'vov. Physics Reports,Volume 229, Issue 3.

4.Robert C. Pullar,Hexagonal ferrites. Progress in Materials Science,Volume 57, Issue 7.