2018年12月11日新西兰Canterbury大学Michael F. Reid 教授学术报告
Electronic and Hyperfine Structure of Rare-Earth Ions in Y2SiO5
One of the challenges for practical quantum-information applications, such as encryption and computation, is the preservation of quantum coherence. Quantum coherence may be stored by making use of the nuclear spins of rare-earth (lanthanide) ions, which are coupled to the electronic states via the hyperfine interaction. Storage of quantum coherence for over six hours using magnetic-hyperfine levels of Eu3+ ions in YSO has been achieved by using the ZEFOZ (ZEro First-Order Zeeman) approach, where the direction and magnitude of an applied magnetic field is adjusted to yield a radio-frequency transition that has no first-order dependence on magnetic field variations, and is thus insensitive to magnetic field inhomogeneity.
Applications development, such as the location of ZEFOZ points, requires accurate modelling of hyperfine and magnetic interactions, which is usually done using a spin Hamiltonian. Spin-Hamiltonian parameters are not transferrable to other electronic states, or to other ions, so each electronic state requires a different spin Hamiltonian. We aim to model electronic and hyperfine energy levels consistently across the rare-earth series using a “crystal field” model. This will enable more efficient investigation of candidates for applications. The lack of symmetry in YSO makes a conventional crystal-field approach impossible. However, by adding magnetic and hyperfine data to remove ambiguities, we have recently shown that it is possible to perform accurate fits for Er3+.
We are now investigating other ions, including Nd3+ and Sm3+, to demonstrate that we can transfer the crystal-field parameters from Er3+ and identify the two different crystallographic sites using Zeeman and laser spectroscopy.
In 1981, Professor Michael F. Reid obtained the Doctor of Philosophy Degree in University of Canterbury (New Zealand). After graduation, he has worded in University of Virginia for three years, then in University of Hong Kong for seven years. In 1993, he returned to New Zeeland and worked in University of Canterbury. His main research interests are the electronic structure and the transition intensities of visible and UV transitions within 4fn configurations and between the 4fn and 4fn-15d configurations of lanthanide (rare-earth) ions in various compounds. Currently, he focuses on the understanding of materials that have potential for quantum-information applications, and on nanoparticles for biomedical imaging. Up to now, he has published more than 160 papers (eg: J. Phys. Chem. C; Phys. Rev. B: Condens. Matter; Appl. Phys. Lett.) and some chapters of several books. His researches are summarized in the following:
(1) Electronic structure and optical properties of lanthanide (rare-earth) materials;
(2) Quantum-information candidate materials;
(3) Nano-particles for biomedical imaging.