Hermann Uys

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The presence of long-range quantum spin correlations underlies a variety of physical phenomena in condensed-matter systems, potentially including high-temperature superconductivity. However, many properties of exotic, strongly correlated spin systems, such as spin liquids, have proved difficult to study, in part because calculations involving N-body(More)
Any quantum system, such as those used in quantum information or magnetic resonance, is subject to random phase errors that can dramatically affect the fidelity of a desired quantum operation or measurement. In the context of quantum information, quantum error correction techniques have been developed to correct these errors, but resource requirements are(More)
We demonstrate spectroscopy and thermometry of individual motional modes in a mesoscopic 2D ion array using entanglement-induced decoherence as a method of transduction. Our system is a ~400 μm-diameter planar crystal of several hundred 9Be(+) ions exhibiting complex drumhead modes in the confining potential of a Penning trap. Exploiting precise control(More)
We provide an introduction to the use of ion crystals in a Penning trap [1, 2, 3, 4] for experiments in quantum information. Macroscopic Penning traps allow for the containment of a few to a few million atomic ions whose internal states may be used in quantum information experiments. Ions are laser Doppler cooled [1], and the mutual Coulomb repulsion of the(More)
In this paper, we report the design, fabrication and preliminary testing of a 150 zone ion trap array built in a 'surface-electrode' geometry micro-fabricated on a single substrate. We demonstrate the transport of atomic ions between the legs of a 'Y'-type junction and measure the in-situ heating rates for the ions. The trap design demonstrates the use of a(More)
A review of ion confinement in Penning traps and discussion of a variety of equilibrium states, including 2D Coulomb crystals (ionic Wigner crystals), can be found in [1–3]. A number of authors have theoretically analyzed and discussed the prospects of using 2D Coulomb crystals for quantum information and computation [4–9]. The engineered Ising interaction,(More)
We introduce concepts from optimal estimation to the stabilization of precision frequency standards limited by noisy local oscillators. We develop a theoretical framework casting various measures for frequency standard variance in terms of frequency-domain transfer functions, capturing the effects of feedback stabilization via a time series of Ramsey(More)
OBJECTIVE Literature on the prevalence and clinical presentation of South African psychiatric HIV positive patients as well as their management is lacking. This study was performed to investigate these parameters. METHOD A prospective study to investigate the prevalence and clinical presentation of HIV positive psychiatric female patients admitted to an(More)
We describe experimental observations of fully developed, large-amplitude bars under the action of a shearing fluid. The experiments were performed in an annular tank filled with water and sheared above by a steady motor source. The same steady shearing flow can produce a variety of different erodible bed manifestations: advective or precessive bars, which(More)
A-G S. Aaronson On perfect completeness for QMA (1&2) 81 G. Adesso Correlation loss & multipartite entanglement across… (7&8) 657 G.G. Amosov Decreasing property of relative entropy & …(7&8) 594 J.-H. An Non-Markovian decoherence dynamics of entangled … (3&4) 317 F. Arguello Quantum wavelet transforms of any order (5&6) 414 N. Bansal Classical appro.(More)