Superconducting Supercomputers and Quantum Computation

Information technologies have been developing at a formidable pace. While miniaturization has been the driver for this in the past decades (Moore\u27s law), the attention is now focusing to the energy consumption. Already a considerable fraction of the worlds\u27 energy use is in information technologies. Also, the on-chip energy dissipation and concomittant high temperatures form a bottleneck in further speeding up processors. For these reasons a great interest exist in the exploration of new computing paradigms. In my presentation, I will introduce two of such paradigms and discuss their current progress and prospects, namely superconducting \u27RSQF\u27 circuitry and quantum-computation. Both technologies require (ultra)-low temperatures, providing interesting challenges for cryogenic engineering

Analysis of low-field isotropic vortex glass containing vortex groups in YBa2Cu3O7−x thin films visualized by scanning SQUID microscopy

The glass-like vortex distribution in pulsed laser deposited YBa2Cu3O7 − x thin films is observed by scanning superconducting quantum interference device microscopy and analysed for ordering after cooling in magnetic fields significantly smaller than the Earth\u27s field. Autocorrelation calculations on this distribution show a weak short-range positional order, while Delaunay triangulation shows a near-complete lack of orientational order. The distribution of these vortices is finally characterised as an isotropic vortex glass. Abnormally closely spaced groups of vortices, which are statistically unlikely to occur, are observed above a threshold magnetic field. The origin of these groups is discussed, but will require further investigation

Structure and magnetic properties of epitaxial CaFe2O4 thin films

CaFe2O4 is a highly anisotropic antiferromagnet reported to display two spin arrangements with up-up-down-down (phase A) and up-down-up-down (phase B) configurations. The relative stability of these phases is ruled by the competing ferromagnetic and antiferromagnetic interactions between Fe3+ spins arranged in two different environments, but a complete understanding of the magnetic structure of this material does not exist yet. In this study we investigate epitaxial CaFe2O4 thin films grown on TiO2 (110) substrates by means of Pulsed Laser Deposition (PLD). Structural characterization reveals the coexistence of two out-of-plane crystal orientations and the formation of three in-plane oriented domains. The magnetic properties of the films, investigated macroscopically as well as locally, including highly sensitive Mossbauer spectroscopy, reveal the presence of just one order parameter showing long-range ordering below T = 185 K and the critical nature of the transition. In addition, a non-zero in-plane magnetization is found, consistent with the presence of uncompensated spins at phase or domain boundaries, as proposed for bulk samples.Comment: Changes are made to take into account the newly published paper by Songvilay et al. (PRB 101,014407) Changes are in last sentence of the abstract, 5th paragraph of the discussion section and conclusions paragrap