1,475 research outputs found
Quantum walk on the line: entanglement and non-local initial conditions
The conditional shift in the evolution operator of a quantum walk generates
entanglement between the coin and position degrees of freedom. This
entanglement can be quantified by the von Neumann entropy of the reduced
density operator (entropy of entanglement). In the long time limit, it
converges to a well defined value which depends on the initial state. Exact
expressions for the asymptotic (long-time) entanglement are obtained for (i)
localized initial conditions and (ii) initial conditions in the position
subspace spanned by the +1 and -1 position eigenstates.Comment: A few mistakes where corrected. One of them leads to a factor of 2 in
eq. (49), the other results remain unchanged. In this version, several
figures where replaced by color version
Effects of non-local initial conditions in the Quantum Walk on the line
We report an enhancement of the decay rate of the survival probability when
non-local initial conditions in position space are considered in the Quantum
Walk on the line. It is shown how this interference effect can be understood
analytically by using previously derived results. Within a restricted position
subspace, the enhanced decay is correlated with a maximum asymptotic
entanglement level while the normal decay rate corresponds to initial relative
phases associated to a minimum entanglement level.Comment: 5 pages, 1 figure, Elsevier style, to appear in Physica
Studies concerning partially reduced nitrogen heterocycles
Carbanion rearrangement studies on selected N-acyl-isoquinoline
and -quinoline Reissert compounds have shown that
alternative intramolecular rearrangements can compete successfully
with the normal 1,2-acyl-migration. The observations have been
rationalised mechanistically and their potential value in
synthesis demonstrated. In particular the formation of a
1-benzoyl-8-hydroxyisoquinoline derivative has been effected
from carbanion rearrangement of the corresponding 8-benzoyloxy
Reissert compound. N-Crotonoylisoquinoline Reissert compound
carbanion and analogous structures have been shown to undergo
a complex reaction in which Michael type attack competes with
the normal migration. [Continues.
Sub-ballistic behavior in quantum systems with L\'evy noise
We investigate the quantum walk and the quantum kicked rotor in resonance
subjected to noise with a L\'evy waiting time distribution. We find that both
systems have a sub-ballistic wave function spreading as shown by a power-law
tail of the standard deviation.Comment: 4 pages, 4 figure
Fellespotten i Regionale forskningsfond – status og utviklingsmuligheter
I denne rapporten presenteres en analyse av den såkalte fellespotten i Regionale forsk-ningsfond. Fellespotten utgjør 15 prosent av de midlene som årlig bevilges til Regionale Forskningsfond, og skal brukes til felles utlysninger i samarbeid mellom regionene for å stimulere til felles satsinger.
Formålet med analysen er å gjennomføre en evaluering av ordningen og fremme forslag om videre utvikling av den
The Crossover beteween Aslamazov-Larkin and Short Wavelength Fluctuations Regimes in HTS Conductivity Experiments
We present paraconductivity (AL) measurements in three different high
temperature superconductors: a melt textured sample, a
epitaxial thin film and a highly textured
tape. The crossovers between different temperature
regimes in excess conductivity have been analysed. The Lawrence-Doniach (LD)
crossover, which separates the 2D and 3D regimes, shifts from lower to higher
temperatures as the compound anisotropy decreases. Once the LD crossover is
overcome, the fluctuation conductivity of the three compounds shows the same
universal behaviour: for all the curves bend down
according to the law. This asymptotic behaviour was
theoretically predicted previously for the high temperature region where the
short wavelength fluctuations (SWF) become important.Comment: 4 pages, Revtex, 1 PostScript figure available upon request
([email protected]); submitted to Physical Review B rapid communication
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