26 research outputs found
Entanglement and quantum state engineering in the optically driven two-electron double-dot structure
We study theoretically the quantum dynamics of two interacting electrons in
the symmetric double-dot structure under the influence of the bichromatic
resonant pulse. The state vector evolution is studied for two different pulse
designs. It is shown that the laser pulse can generate the effective exchange
coupling between the electron spins localized in different dots. Possible
applications of this effect to the quantum information processing (entanglement
generation, quantum state engineering) are discussed.Comment: 28 pages, 3 figure
Quantum register based on structured diamond waveguide with NV centers
We propose a scheme of quantum information processing with NV-centers
embedded inside diamond nanostructure. Single NV-center placed in the cavity
plays role of an electron spin qubit which evolution is controlled by microwave
pulses. Besides, it couples to the cavity field via optical photon exchange. In
their turn, neighbor cavities are coupled to each other through the photon
hopping to form a bus waveguide mode. This waveguide mode overlaps with all
NV-centers. Entanglement between distant centers is organized by appropriate
tuning of their optical frequency relative to the waveguide frequency via
electrostatic control without lasers. We describe the controlled-Z operation
that is by one order of magnitude faster than in off-resonant laser-assisted
schemes proposed earlier. Spectral characteristics of the one-dimensional chain
of microdisks are calculated by means of numerical modeling, using the approach
analogous to the tight-binding approximation in the solid-state physics. The
data obtained allow to optimize the geometry of the microdisk array for the
effective implementation of quantum operations.Comment: to be published in Proc. of SPI
Rabi oscillations in the four-level double-dot structure under the influence of the resonant pulse
We study theoretically the quantum dynamics of an electron in the symmetric
four-level double-dot structure under the influence of the monochromatic
resonant pulse. The probability amplitudes of the eigenstates relevant for the
quantum dynamics are found from the solution of the non-stationary
Schr\"odinger equation. The first-order correction term to the solution
obtained through the rotating wave approximation is calculated. The three-level
double-dot dynamics and the two-level single-dot dynamics, as well as the
off-resonant excitation process, are derived from the general formulae for
corresponding choices of the pulse and structure parameters. The results
obtained may be applied to the solid-state qubit design.Comment: Accepted for publication in Phys. Rev.
Single-qubit operations in the double-donor structure driven by optical and voltage pulses
We study theoretically the quantum dynamics of an electron in the
singlyionized double-donor structure in the semiconductor host under the
influence of laser pulses whose frequencies are close to structure resonant
frequencies. This system can be used as a charge qubit where the logical states
are defined by the lowest two energy states of the remaining valence electron
localized around one or another donor. The quantum operations are performed via
resonant or Raman-like transitions between the localized (qubit) states and the
excited states delocalized over the structure, combined with phase shifts
between qubit states generated by voltage pulses. The possibility of
realization of arbitrary single-qubit rotations is demonstrated.Comment: to appear in Phys. Rev.
Acylated 2-(N-arylaminomethylene)benzo[b]thiophene-3(2H)-Ones: Molecular Switches with Varying Migrants and Substituents
Synthesis and properties of photochromic acylated 2-(N-arylaminomethylene)benzo[b]thiophene-3(2H)-ones are described. Their structure largely depends on the nature of acyl migrant and in a less degree on N-aryl substituent
Synthesis of Novel Iono- and Photochromic Spiropyrans Derived from 6,7-Dihydroxy-8-Formyl-4-Methyl-2H-Chromene-2-One
Novel photochromic spiropyrans (SPPs) containing 6′-hydroxy group were synthesized and their spectral properties as well as abilities for complexation with metal ions studied. In solutions they exist as equilibrium mixture of spirocyclic (A) and merocyanine (B) isomers. The largest content of merocyanine form was found for the derivative with an electron-donating methyl group in position 5 of hetaryl fragment. The irradiation of SPPs in acetonitrile shifts the equilibrium to the B form. Similar effect causes the addition of metal cations due to formation of colored complexes with merocyanine isomers
The Helicobacter pylori Genome Project : insights into H. pylori population structure from analysis of a worldwide collection of complete genomes
Helicobacter pylori, a dominant member of the gastric microbiota, shares co-evolutionary history with humans. This has led to the development of genetically distinct H. pylori subpopulations associated with the geographic origin of the host and with differential gastric disease risk. Here, we provide insights into H. pylori population structure as a part of the Helicobacter pylori Genome Project (HpGP), a multi-disciplinary initiative aimed at elucidating H. pylori pathogenesis and identifying new therapeutic targets. We collected 1011 well-characterized clinical strains from 50 countries and generated high-quality genome sequences. We analysed core genome diversity and population structure of the HpGP dataset and 255 worldwide reference genomes to outline the ancestral contribution to Eurasian, African, and American populations. We found evidence of substantial contribution of population hpNorthAsia and subpopulation hspUral in Northern European H. pylori. The genomes of H. pylori isolated from northern and southern Indigenous Americans differed in that bacteria isolated in northern Indigenous communities were more similar to North Asian H. pylori while the southern had higher relatedness to hpEastAsia. Notably, we also found a highly clonal yet geographically dispersed North American subpopulation, which is negative for the cag pathogenicity island, and present in 7% of sequenced US genomes. We expect the HpGP dataset and the corresponding strains to become a major asset for H. pylori genomics