Quantum Entanglement of Anisotropic Magnetic Nanodots

Physical systems for quantum computing considered at present operate at very low temperatures, typically much smaller than 1 K, but in the future it will be necessary to move towards finite-temperature mechanisms. Among the systems of current interest are spin chains and spin clusters with exchange anisotropy, where zero- and finite-temperature quantum states can be tuned by an external magnetic field [1, 2]. However, the smallness of the Bohr magneton, corresponding to 0.672 K/T, makes it difficult to exploit magnetic fields at temperatures above 4.2 K, and exchange anisotropy is a small and difficult-to-realize relativistic correction to the isotropic exchange. Here we analyze a mesoscopic two-dot system whose basic level splitting is realized by magnetocrystalline anisotropy and determine the qubit entanglement between the dot's lowest-lying states. The anisotropy is relatively easy to tune and leads to a pronounced and temperature-dependent resonant entanglement. - This research is supported by ARO, NSF-MRSEC, the W. M. Keck Foundation, and CMRA.