48 research outputs found
Majorana-based fermionic quantum computation
Because Majorana zero modes store quantum information non-locally, they are
protected from noise, and have been proposed as a building block for a quantum
computer. We show how to use the same protection from noise to implement
universal fermionic quantum computation. Our architecture requires only two
Majoranas to encode a fermionic quantum degree of freedom, compared to
alternative implementations which require a minimum of four Majoranas for a
spin quantum degree of freedom. The fermionic degrees of freedom support both
unitary coupled cluster variational quantum eigensolver and quantum phase
estimation algorithms, proposed for quantum chemistry simulations. Because we
avoid the Jordan-Wigner transformation, our scheme has a lower overhead for
implementing both of these algorithms, and the simulation of Trotterized
Hubbard Hamiltonian in time per unitary step. We finally
demonstrate magic state distillation in our fermionic architecture, giving a
universal set of topologically protected fermionic quantum gates.Comment: 4 pages + 4 page appendix, 4 figures, 2 table
Orbital similarity functions - application to asteroid pairs
The paper expands the idea of Vokrouhlický and Nesvorný who used a modified Zappalà et al. metric with osculating elements in search for pairs of asteroids suspected of having a common origin. Using six different orbital similarity functions, we find that five of them display a similar excess of close pairs in the catalogue of osculating elements. The excess is even higher when mean orbital elements are used. Similarly, when the mean elements are applied, there is a better agreement between the closest pairs found in the same catalogue using different metrics. The common subset of 62 pairs from five lists of 100 closest pairs according to different distance functions is provided. Investigating an artificial sample of asteroid orbital pairs with a known initial orbital velocity difference we find that the Drummond metric best preserves orbital proximity over long time intervals
Development of the interatrial wall during the ontogenesis of foetuses and children up to one year of age
Background: The foramen ovale, present in foetal interatrial septum, plays an important role during foetal life. During delivery, foramen ovale closes and becomes fossa ovalis, starting the pulmonary circulation. The aim of our study was to describe the growth of the interatrial wall and changes in location of the foramen ovale, and fossa ovalis during the ontogenesis in the human hearts.Materials and methods: The study was performed on post-mortem material obtained from 92 human hearts from 22nd week of foetal life up to 1 year of age, fixed in a 4% formalin solution.Results: The interatrial wall size in the studied development period was greater in the horizontal than in the vertical dimension. During ontogenesis up to 1 year old, the anterior and inferior parts of the interatrial wall increased their shares considerably by 8% and 6%, respectively. The percentage participation of foramen ovale in the interatrial wall construction in the foetal period formed more than 50% of its size and fairly decreased reaching in infants about 39%.Conclusions: Our study demonstrated that during ontogenesis, from the foetal period to infancy, the parts of the interatrial wall increase their dimensions unevenly. The foramen ovale growth is smaller, compared to the rest of the interatrial wall development. On the basis of our data we can assume that the foramen ovale centre tends to be found in the postero-inferior quadrant of the interatrial wall (foetuses) and in postero-superior quadrant of the interatrial wall — in infants
New results on the pd --> 3He eta production near threshold
Measurements on the eta meson production in proton-deuteron collisions have
been performed using the COSY-11 facility at COSY Juelich. Here we present
preliminary results on total and differential cross sections for the pd --> 3He
eta reaction at five excess energies between Q = 5.1 and Q = 40.6 MeV. The
obtained angular distributions for the emitted eta mesons in the center of mass
system expose a transition from an almost isotropic emission to a highly
anisotropic distribution. The extracted total cross sections support a strong
eta-3He final state interaction and will be compared with model predictions.Comment: Presented at MESON 2004: 8th International Workshop on Meson
Production, Properties and Interactions, Cracow, Poland, 4-8 Jun 2004, 3
pages, Submitted to Int. J. Mod. Phys.
Threshold Hyperon Production at COSY-11
The Lambda, Sigma0 and Sigma+ hyperon production in NN collisions is studied
at the COSY - 11 installation in order to investigate the production mechanism
as well as to extract information about the Y-N interaction.Comment: 3 pages, 2 figure
Production of Eta Mesons in Proton-Proton Collisions Close to Threshold
A brief experimental overview on the close-to-threshold eta meson production
in proton-proton interactions is presented and the available observables in
measurements with unpolarized and polarized beam and target are discussed.Comment: 4 pages; Presented at Meson 2004: 8th International Workshop on Meson
Production, Properties and Interaction, Krakow, Poland, 4-8 June 2004;
Submitted to International Journal of Modern Physics
Near threshold eta meson production in dp collisions
Preliminary results of recent measurements of the near threshold eta meson
production in the dp-->dp eta reaction are presented. The experiment was
performed at the COSY-Juelich accelerator with the use of the COSY-11 detection
system. Data were taken for three values of deuteron beam momenta corresponding
to excess energies of 3.2, 6.1 and 9.2 MeV. The energy dependence of the total
cross section confirms a strong effect of the final state interaction.Comment: Talk given at 9th International Workshop on Meson Production,
Properties and Interaction, Cracow, Poland, 9-13 June 2006. 5 pages, 3
figure
Study of the production mechanism of the eta meson by means of analysing power measurements
Information about the production mechanism of the eta meson in proton-proton
collisions can be inferred by confronting the experimental studies on the
analysing power for the p(pol)p --> pp eta reaction with the theoretical
predictions of this observable. Results show that the predictions of pure
pseudoscalar- or vector meson exchange model are insufficient to describe the
analysing powers.Comment: 4 pages, 4 figures, Presented at MESON 2006: 9th International
Workshop on Meson Production, Properties and Interactions, Cracow, Poland,
9-13 Jun 200
Search for Bremsstrahlung radiation in quasi-free n p --> n p gamma reactions
Due to the high sensitivity of the N N --> N N gamma reaction to the
nucleon-nucleon potential, Bremsstrahlung radiation is used as a tool to
investigate details of the nucleon-nucleon interaction. Such investigations can
be performed at the cooler synchrotron COSY in the Research Centre Juelich, by
dint of the COSY-11 detection system. The results of the identification of
Bremsstrahlung radiation emitted via the d p --> d p gamma reaction in data
taken with a proton target and a deuteron beam are presented and discussed.Comment: 3 pages; Presented at Meson 2004: 8th International Workshop on Meson
Production, Properties and Interaction, Krakow, Poland, 4-8 June 2004;
Submitted to International Journal of Modern Physics
Drift chamber with a c-shaped frame
We present the construction of a planar drift chamber with wires stretched
between two arms of a c-shaped aluminium frame. The special shape of the frame
allows to extendthe momentum acceptance of the COSY-11 detection system towards
lower momenta without suppressing the high momentum particles. The proposed
design allows for construction of tracking detectors covering small angles with
respect to the beam, which can be installed and removed without dismounting the
beam-pipe. For a three-dimensional track reconstruction a computer code was
developed using a simple algorithm of hit preselection.Comment: submitted to Nucl. Instr. & Meth