40,475 research outputs found
Txt2vz: a new tool for generating graph clouds
We present txt2vz (txt2vz.appspot.com), a new tool for automatically generating a visual summary of unstructured text data found in documents or web sites. The main purpose of the tool is to give the user information about the text so that they can quickly get a good idea about the topics covered. Txt2vz is able to identify important concepts from unstructured text data and to reveal relationships between those concepts. We discuss other approaches to generating diagrams from text and highlight the differences between tag clouds, word clouds, tree clouds and graph clouds
Sub-barrier Coulomb effects on the interference pattern in tunneling ionization photoelectron spectra
We use a quantum trajectory-based semi-classical method to account for
Coulomb interaction between the photoelectron and the parent ion in the
classically forbidden, sub-barrier region during strong-field tunneling
ionization processes. We show that---besides the well-known modification of the
tunneling ionization probability---there is also an influence on the
interference pattern in the photoelectron spectra. In the long-wavelength
limit, the shift of the intra-cycle interference fringes caused by sub-barrier
Coulomb effects in the laser polarization direction can be derived
analytically. We compare our results with \emph{ab initio} solutions of the
time-dependent Schr\"odinger equation and find good agreement in the
long-wavelength regime, whereas the standard strong field approximation fails.
We show that the nodal structure along low-order above-threshold ionization
rings is also affected by sub-barrier Coulomb effects.Comment: 10 pages, 4 figures, RevTe
Universal Quantum Degeneracy Point for Superconducting Qubits
The quantum degeneracy point approach [D. Vion et al., Science 296, 886
(2002)] effectively protects superconducting qubits from low-frequency noise
that couples with the qubits as transverse noise. However, low-frequency noise
in superconducting qubits can originate from various mechanisms and can couple
with the qubits either as transverse or as longitudinal noise. Here, we present
a quantum circuit containing a universal quantum degeneracy point that protects
an encoded qubit from arbitrary low-frequency noise. We further show that
universal quantum logic gates can be performed on the encoded qubit with high
gate fidelity. The proposed scheme is robust against small parameter spreads
due to fabrication errors in the superconducting qubits.Comment: 7 pages, 4 figure
Adiabatic State Conversion and Pulse Transmission in Optomechanical Systems
Optomechanical systems with strong coupling can be a powerful medium for
quantum state engineering. Here, we show that quantum state conversion between
cavity modes with different wavelengths can be realized with high fidelity by
adiabatically varying the effective optomechanical couplings. The fidelity for
the conversion of gaussian states is derived by solving the Langevin equation
in the adiabatic limit. We also show that photon pulses can be transmitted
between input-output channels with different wavelengths via the effective
optomechanical couplings and the output pulse shape can also be manipulated.Comment: 5 pages, 2 figures. Supplementary Materials at
http://prl.aps.org/supplemental/PRL/v108/i15/e15360
The HI absorption distance of HESS J1943+213 favours its extragalactic nature
The H.E.S.S. collaboration (Abramowski et al. 2011) dicovered a new TeV
point-like source HESS J1943+213 in the Galactic plane and suggested three
possible low-energy-band counterparts: a -ray binary, a pulsar wind
nebula (PWN), or a BL Lacertae object. We measure the distance to the radio
counterpart G57.76-1.29 of HESS J1943+213. We analyze Very Large Array
observations to obtain a reliable HI absorption spectrum.The resulting distance
limit is 16 kpc. This distance strongly supports that HESS J1943+213 is
an extragalactic source, consistent with the preferred counterpart of the HESS
collaboration.Comment: 3 figures, 2 pages, A&A accepte
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