1,604 research outputs found
Strongly trapped two-dimensional quantum walks
Discrete time quantum walks (DTQWs) are nontrivial generalizations of random
walks with a broad scope of applications. In particular, they can be used as
computational primitives, and they are suitable tools for simulating other
quantum systems. DTQWs usually spread ballistically due to their quantumness.
In some cases, however, they can remain localized at their initial state
(trapping). The trapping and other fundamental properties of DTQWs are
determined by the choice of the coin operator. We introduce and analyze an up
to now uncharted type of walks driven by a coin class leading to strong
trapping, complementing the known list of walks. This class of walks exhibit a
number of exciting properties with the possible applications ranging from light
pulse trapping in a medium to topological effects and quantum search.Comment: 5 pages, 4 figures, Accepted for publication in Physical Review
Binding of Oxovanadium(IV) Complexes to Blood Serum Albumins
In this work the binding of VIVO2+ and VIVO-complexes to
serum albumins {human serum albumin (HSA), bovine serum albumin
(BSA) and porcine serum albumin (PSA)} are studied using circular
dichroism (CD), electron paramagnetic resonance (EPR) and visible
absorption spectroscopy. The results confirm previous findings that
VIVO2+ occupies at least two types of binding sites on albumin: ‘the
strong vanadium binding site’ (designated by VBS1) and ‘the weak
vanadium binding sites’ (designated by VBS2). VBS1 binds 1 mol
equivalent of VIVO2+. On the other hand VBS2 correspond to binding
of several mol equivalents of VIVO, and studies done with PSA in the
presence of excess ZnII ions indicate that VSB2 corresponds to two
distinct types of sites. The hyperfine coupling constant Az for VIVO2+
binding at VBS2 on HSA and BSA are all very similar (~168 × 10-4
cm-1) but differ slightly on PSA (~166 × 10-4 cm-1) due to differences
in the binding sets. When (VIVO)-HSA systems are titrated with maltol
ternary species of (maltol)m(VIVO)mHSA and (maltol)2m(VIVO)mHSA
stoichiometry form which are clearly distinguishable from the binary
(VIVO)-HSA system by the type and intensity of the CD spectra
recorded. Changes are also observable in the intensity of the X-band
EPR spectra, but not much in the hyperfine coupling constants Az,
which are all in the range 166-167 × 10-4 cm-1. The results further
demonstrate that the presence of maltol may enhance the binding of
VIVO to albumin
Discrete time quantum walks on percolation graphs
Randomly breaking connections in a graph alters its transport properties, a
model used to describe percolation. In the case of quantum walks, dynamic
percolation graphs represent a special type of imperfections, where the
connections appear and disappear randomly in each step during the time
evolution. The resulting open system dynamics is hard to treat numerically in
general. We shortly review the literature on this problem. We then present our
method to solve the evolution on finite percolation graphs in the long time
limit, applying the asymptotic methods concerning random unitary maps. We work
out the case of one dimensional chains in detail and provide a concrete, step
by step numerical example in order to give more insight into the possible
asymptotic behavior. The results about the case of the two-dimensional integer
lattice are summarized, focusing on the Grover type coin operator.Comment: 22 pages, 3 figure
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