Author : Rose Ahlefeldt
Publisher :
ISBN 13 :
Total Pages : 438 pages
Book Rating : 4.:/5 (896 download)
Book Synopsis Evaluation of a Stoichiometric Rare Earth Crystal for Quantum Computing by : Rose Ahlefeldt
Download or read book Evaluation of a Stoichiometric Rare Earth Crystal for Quantum Computing written by Rose Ahlefeldt and published by . This book was released on 2013 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a spectroscopic study of the 7F0-5D0 transition of Eu3+ in EuCl3.6H2O, which is used to evaluate the potential performance of a quantum computing system implemented in EuCl3.6H2O and, more generally, in stoichiometric rare earth crystals. EuCl3.6H2O has one of the narrowest optical inhomogeneous linewidths of any solid but this linewidth is shown to be still much larger than that required for practical quantum computing in a rare earth crystal. To assess the possibility of reducing the linwidth, the contributions of isotopic impurities to both the optical linewidth and line structure were investigated, and ligand isotopes were identified as a major source of both inhomogeneous broadening and structure on the optical transition, suggesting that the linewidth could be substantially reduced by isotopically purifying EuCl3.6H2O. The effect of ligand isotopes on the optical lifetime and coherence time was also investigated. It was found that fully deuterating the crystal to EuCl3.6D2O substantially improves both the lifetime and coherence time. The satellite lines formed in the optical spectrum of a rare earth crystal when it is doped with another rare earth are proposed as qubits. A crucial step in characterising EuCl3.6H2O for quantum computing is associating these satellite lines in EuCl3.6H2O with crystallographic sites. A new method for associating sites with lines, which works for low symmetry crystals such as EuCl3.6H2O, is presented. This method involves modelling the splitting of the ground state hyperfine levels caused by the magnetic dipole-dipole interaction between a Kramers dopant and the Eu3+ ion. Using this method, most of the outer satellite lines in rare earth doped EuCl3.6H2O were assigned to crystallographic sites. It has been proposed that the electronic interactions between these satellite lines be used to enact two-qubit gates in a rare earth quantum computer. These interactions were measured between a number of different satellite lines using a new two-laser spectral holeburning technique. Interactions of up to 46.081 +- 0.005 MHz were observed, and this was the first time that electronic interactions between weakly coupled rare earth ions had been measured. The two most common interactions identified between rare earth ions in solids are electric dipole-dipole and exchange, but the observed interactions are stronger than expected from a electric dipole-dipole model and occur at too large a distance to be superexchange. It is shown that the development of a moderate-sized quantum processor, one with more than 10 qubits, in a stoichiometric rare earth crystal is feasible provided that the optical inhomogeneous linewidth is reduced below 1 MHz. Demonstrations of three or four qubit devices should be possible using existing materials.
