Spin-Orbit Qubits of Rare-Earth-Metal Ions in Axially Symmetric Crystal Fields

摘要

Contrary to the well-known spin qubits, rare-earth-metal qubits are characterized by a strong influence of crystal field due to large spin-orbit coupling. At low temperature and in the presence of resonance microwaves, it is the magnetic moment of the crystal-field ground state which nutates (for several μs) and the Rabi frequency Ω_R is anisotropic. Here, we present a study of the variations of Ω_R(H_0) with the magnitude and direction of the static magnetic field H_0 for the odd ~(167)Er isotope in a single crystal CaWO_4:Er~(3+). The hyperfine interactions split the Ω_R(H_0) curve into eight different curves which are fitted numerically and described analytically. These "spin-orbit qubits" should allow detailed studies of decoherence mechanisms which become relevant at high temperature and open new ways for qubit addressing using properly oriented magnetic fields.