2,190 research outputs found
Two-photon interference between disparate sources for quantum networking
Quantum networks involve entanglement sharing between multiple users.
Ideally, any two users would be able to connect regardless of the type of
photon source they employ, provided they fulfill the requirements for
two-photon interference. From a theoretical perspective, photons coming from
different origins can interfere with a perfect visibility, provided they are
made indistinguishable in all degrees of freedom. Previous experimental
demonstrations of such a scenario have been limited to photon wavelengths below
900 nm, unsuitable for long distance communication, and suffered from low
interference visibility. We report two-photon interference using two disparate
heralded single photon sources, which involve different nonlinear effects,
operating in the telecom wavelength range. The measured visibility of the
two-photon interference is 80+/-4%, which paves the way to hybrid universal
quantum networks
Pressure-induced amorphization and polyamorphism in one-dimensional single crystal TiO2 nanomaterials
The structural phase transitions of single crystal TiO2-B nanoribbons were
investigated in-situ at high-pressure using the synchrotron X-ray diffraction
and the Raman scattering. Our results have shown a pressure-induced
amorphization (PIA) occurred in TiO2-B nanoribbons upon compression, resulting
in a high density amorphous (HDA) form related to the baddeleyite structure.
Upon decompression, the HDA form transforms to a low density amorphous (LDA)
form while the samples still maintain their pristine nanoribbon shape. HRTEM
imaging reveals that the LDA phase has an {\alpha}-PbO2 structure with short
range order. We propose a homogeneous nucleation mechanism to explain the
pressure-induced amorphous phase transitions in the TiO2-B nanoribbons. Our
study demonstrates for the first time that PIA and polyamorphism occurred in
the one-dimensional (1D) TiO2 nanomaterials and provides a new method for
preparing 1D amorphous nanomaterials from crystalline nanomaterials.Comment: 4 figure
Nesting properties and anomalous band effect in MgB2
First principle FLAPW band calculations of the new superconductor MgB2 were
performed and the polarization function P12(Q) between the two p-bands mainly
formed of boron pz-orbital was calculated. We found that P12(Q) is
substantially enhanced around Q=(0,0,p/c), which supports the two-band
mechanism of superconductivity for MgB2. P12(Q) peaks at Qz ~ 0.3(2p/c) and Qz
\~ 0.5(2p/c). These two peaks are related to the nesting of these Fermi
surfaces, but significantly deviates from the position expected from the
simplest tight-binding bands for the p-bands. From the calculations for
different lattice parameters, we have found significant dependences on the
isotopic species of B and on the pressure effect of the polarization function
in accordance with the respective changes of Tc in the above-mentioned
framework.Comment: 15 pages, 7 graphs. to be published in J. Phys. Soc. Jpn. 70_, No.
Random Fixed Point of Three-Dimensional Random-Bond Ising Models
The fixed-point structure of three-dimensional bond-disordered Ising models
is investigated using the numerical domain-wall renormalization-group method.
It is found that, in the +/-J Ising model, there exists a non-trivial fixed
point along the phase boundary between the paramagnetic and ferromagnetic
phases. The fixed-point Hamiltonian of the +/-J model numerically coincides
with that of the unfrustrated random Ising models, strongly suggesting that
both belong to the same universality class. Another fixed point corresponding
to the multicritical point is also found in the +/-J model. Critical properties
associated with the fixed point are qualitatively consistent with theoretical
predictions.Comment: 4 pages, 5 figures, to be published in Journal of the Physical
Society of Japa
Proximity effect in ultrathin Pb/Ag multilayers within the Cooper limit
We report on transport and tunneling measurements performed on ultra-thin
Pb/Ag (strong coupled superconductor/normal metal) multilayers evaporated by
quench condensation. The critical temperature and energy gap of the
heterostructures oscillate with addition of each layer, demonstrating the
validity of the Cooper limit model in the case of multilayers. We observe
excellent agreement with a simple theory for samples with layer thickness
larger than 30\AA . Samples with single layers thinner than 30\AA deviate from
the Cooper limit theory. We suggest that this is due to the "inverse proximity
effect" where the normal metal electrons improve screening in the
superconducting ultrathin layer and thus enhance the critical temperature.Comment: 4 pages, 4 figure
Boron Isotope Effect in Superconducting MgB
We report the preparation method of, and boron isotope effect for MgB, a
new binary intermetallic superconductor with a remarkably high superconducting
transition temperature (B) = 40.2 K. Measurements of both
temperature dependent magnetization and specific heat reveal a 1.0 K shift in
between MgB and MgB. Whereas such a high transition
temperature might imply exotic coupling mechanisms, the boron isotope effect in
MgB is consistent with the material being a phonon-mediated BCS
superconductor.Comment: One figure and related discussion adde
Gyrokinetic simulations of microturbulence in tokamak plasmas presenting an electron internal transport barrier, and development of a global version of the GENE code
The abstract goes here
Off-Equilibrium Dynamics in Finite-Dimensional Spin Glass Models
The low temperature dynamics of the two- and three-dimensional Ising spin
glass model with Gaussian couplings is investigated via extensive Monte Carlo
simulations. We find an algebraic decay of the remanent magnetization. For the
autocorrelation function a typical
aging scenario with a scaling is established. Investigating spatial
correlations we find an algebraic growth law of
the average domain size. The spatial correlation function scales with . The sensitivity of the
correlations in the spin glass phase with respect to temperature changes is
examined by calculating a time dependent overlap length. In the two dimensional
model we examine domain growth with a new method: First we determine the exact
ground states of the various samples (of system sizes up to )
and then we calculate the correlations between this state and the states
generated during a Monte Carlo simulation.Comment: 38 pages, RevTeX, 14 postscript figure
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