93 research outputs found
Quantum state transfer with untuneable couplings
We present a general scheme for implementing bi-directional quantum state
transfer in a quantum swapping channel. Unlike many other schemes for quantum
computation and communication, our method does not require qubit couplings to
be switched on and off. The only control variable is the bias acting on
individual qubits. We show how to derive the parameters of the system (fixed
and variable) such that perfect state transfer can be achieved. Since these
parameters vary linearly with the pulse width, our scheme allows flexibility in
the time scales under which qubits evolve. Unlike quantum spin networks, our
scheme allows the transmission of several quantum states at a time, requiring
only a two qubit separation between quantum states. By pulsing the biases of
several qubits at the same time, we show that only eight bias control lines are
required to achieve state transfer along a channel of arbitrary length.
Furthermore, when the information to be transferred is purely classical in
nature, only three bias control lines are required, greatly simplifying the
circuit complexity
Constraints on Low-Mass WIMP Interactions on 19F from PICASSO
Recent results from the PICASSO dark matter search experiment at SNOLAB are
reported. These results were obtained using a subset of 10 detectors with a
total target mass of 0.72 kg of 19F and an exposure of 114 kgd. The low
backgrounds in PICASSO allow recoil energy thresholds as low as 1.7 keV to be
obtained which results in an increased sensitivity to interactions from Weakly
Interacting Massive Particles (WIMPs) with masses below 10 GeV/c^2. No dark
matter signal was found. Best exclusion limits in the spin dependent sector
were obtained for WIMP masses of 20 GeV/c^2 with a cross section on protons of
sigma_p^SD = 0.032 pb (90% C.L.). In the spin independent sector close to the
low mass region of 7 GeV/c2 favoured by CoGeNT and DAMA/LIBRA, cross sections
larger than sigma_p^SI = 1.41x10^-4 pb (90% C.L.) are excluded.Comment: 23 pages, 7 figures, to be published in Phys. Lett.
Electron/pion separation with an Emulsion Cloud Chamber by using a Neural Network
We have studied the performance of a new algorithm for electron/pion
separation in an Emulsion Cloud Chamber (ECC) made of lead and nuclear emulsion
films. The software for separation consists of two parts: a shower
reconstruction algorithm and a Neural Network that assigns to each
reconstructed shower the probability to be an electron or a pion. The
performance has been studied for the ECC of the OPERA experiment [1].
The separation algorithm has been optimized by using a detailed Monte
Carlo simulation of the ECC and tested on real data taken at CERN (pion beams)
and at DESY (electron beams). The algorithm allows to achieve a 90% electron
identification efficiency with a pion misidentification smaller than 1% for
energies higher than 2 GeV
Currículo e saberes docentes: o que aprendemos pesquisando leitura e escrita em três escolas de formação de professores
O artigo se baseia em pesquisa sobre leitura e escrita de professores. Fundamenta-se na perspectiva da teoria crítica da cultura. Analisa a escrita e a leitura de futuros professores de três escolas de formação docente. Amplia a reflexão com questionamentos e recomendações a respeito de políticas públicas de formação de professores
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