9,072 research outputs found
Critical Properties of the transition between the Haldane phase and the large-D phase of the spin-1/2 ferromagnetic-antiferromagnetic Heisenberg chain with on-site anisotropy"
We analytically study the ground-state quantum phase transition between the
Haldane phase and the large- (LD) phase of the
ferromagnetic-antiferromagnetic alternating Heisenberg chain with on-site
anisotropy. We transform this model into a generalized version of the
alternating antiferromagnetic Heisenberg model with anisotropy. In the
transformed model, the competition between the transverse and longitudinal bond
alternations yields the Haldane-LD transition. Using the bosonization method,
we show that the critical exponents vary continuously on the Haldane-LD
boundary. Our scaling relations between critical exponents very well explains
the numerical results by Hida.Comment: text 12 pages (Plain TeX), LaTeX sourse files of a table and a figure
on reques
Demonstration of an optical quantum controlled-NOT gate without path interference
We report the first experimental demonstration of an optical quantum
controlled-NOT gate without any path interference, where the two interacting
path interferometers of the original proposals (Phys. Rev. A {\bf 66}, 024308
(2001), Phys. Rev. A {\bf 65}, 012314 (2002)) have been replaced by three
partially polarizing beam splitters with suitable polarization dependent
transmittances and reflectances. The performance of the device is evaluated
using a recently proposed method (Phys. Rev. Lett. {\bf 94}, 160504 (2005)), by
which the quantum process fidelity and the entanglement capability can be
estimated from the 32 measurement results of two classical truth tables,
significantly less than the 256 measurement results required for full quantum
tomography.Comment: 4 pages, 3 figure
Formal Relation among Various Hermitian and non-Hermitian Effective Interactions
A general definition of the model-space effective interaction is given. The
energy-independent effective hamiltonians derived in a time-independent way are
classified systematically.Comment: To appear in IJMPE; Proceedings of "Blueprints for the Nucleus,"
Istanbul, Turkey, May 200
Realization of a Knill-Laflamme-Milburn C-NOT gate -a photonic quantum circuit combining effective optical nonlinearities
Quantum information science addresses how uniquely quantum mechanical
phenomena such as superposition and entanglement can enhance communication,
information processing and precision measurement. Photons are appealing for
their low noise, light-speed transmission and ease of manipulation using
conventional optical components. However, the lack of highly efficient optical
Kerr nonlinearities at single photon level was a major obstacle. In a
breakthrough, Knill, Laflamme and Milburn (KLM) showed that such an efficient
nonlinearity can be achieved using only linear optical elements, auxiliary
photons, and measurement. They proposed a heralded controlled-NOT (CNOT) gate
for scalable quantum computation using a photonic quantum circuit to combine
two such nonlinear elements. Here we experimentally demonstrate a KLM CNOT
gate. We developed a stable architecture to realize the required four-photon
network of nested multiple interferometers based on a displaced-Sagnac
interferometer and several partially polarizing beamsplitters. This result
confirms the first step in the KLM `recipe' for all-optical quantum
computation, and should be useful for on-demand entanglement generation and
purification. Optical quantum circuits combining giant optical nonlinearities
may find wide applications across telecommunications and sensing.Comment: 6pages, 3figure
Fabrication of FeSi and Fe3Si compounds by electron beam induced mixing of [Fe/Si]2 and [Fe3/Si]2 multilayers grown by focused electron beam induced deposition
Fe-Si binary compounds have been fabricated by focused electron beam induced
deposition by the alternating use of iron pentacarbonyl, Fe(CO)5, and
neopentasilane, Si5H12 as precursor gases. The fabrication procedure consisted
in preparing multilayer structures which were treated by low-energy electron
irradiation and annealing to induce atomic species intermixing. In this way we
are able to fabricate FeSi and Fe3Si binary compounds from [Fe=Si]2 and
[Fe3=Si]2 multilayers, as shown by transmission electron microscopy
investigations. This fabrication procedure is useful to obtain nanostructured
binary alloys from precursors which compete for adsorption sites during growth
and, therefore, cannot be used simultaneously
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