917 research outputs found
Quantum Spin Dimers from Chiral Dissipation in Cold-Atom Chains
We consider the non-equilibrium dynamics of a driven dissipative spin chain
with chiral coupling to a 1D bosonic bath, and its atomic implementation with a
two-species mixture of cold quantum gases. The reservoir is represented by a
spin-orbit coupled 1D quasi-condensate of atoms in a magnetized phase, while
the spins are identified with motional states of a separate species of atoms in
an optical lattice. The chirality of reservoir excitations allows the spins to
couple differently to left and right moving modes, which in our atomic setup
can be tuned from bidirectional to purely unidirectional. Remarkably, this
leads to a pure steady state in which pairs of neighboring spins form dimers
that decouple from the remainder of the chain. Our results also apply to
current experiments with two-level emitters coupled to photonic waveguides.Comment: Replaced by published version (6 pages + 8 pages supplemental
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Direct Metal Laser Fabrication of Cu Slabs from Powder Precursor: Surface Depth of Melt and Furnace Temperature Issues
A DMLF processing unit based on a raster-scanned 80 W CO2 laser beam has been
developed to process single layers of metallic powder precursor. The process chamber
provides atmosphere control (high vacuum and inert gas refill) besides temperature
elevation up to 700 o
C. In this work, copper powder precursor is confined inside a
refractory steel mask surrounded by an aluminum oxide jacket that acts as insulator. The
powder layers can have thicknesses of 0,5 and 1 mm. An infrared pyrometer measures
in real time the temperature at one location in the surface of the powder bed. Scan
speed, scan step, and furnace temperature have been varied to find combinations of such
parameters that render surface melting and maximum densification. Partially melted
samples were produced and their mass density was measured. Micro-hardness and
surface roughness were also measured along the resolidified surface, the first rendering
an average of 80,6 HV compared to the 90-105 HV of oxygen free copper, while the
second resulting in an 8 μm Ra value. Maximum melt of depth achieved is ~0,15 mm
followed by a sintered layer.Mechanical Engineerin
Nonlinear Quantum Optomechanics via Individual Intrinsic Two-Level Defects
We propose to use the intrinsic two-level system (TLS) defect states found
naturally in integrated optomechanical devices for exploring cavity QED-like
phenomena with localized phonons. The Jaynes-Cummings-type interaction between
TLS and mechanics can reach the strong coupling regime for existing
nano-optomechanical systems, observable via clear signatures in the
optomechanical output spectrum. These signatures persist even at finite
temperature, and we derive an explicit expression for the temperature at which
they vanish. Further, the ability to drive the defect with a microwave field
allows for realization of phonon blockade, and the available controls are
sufficient to deterministically prepare non-classical states of the mechanical
resonator.Comment: Comments welcome (5+7 pages), Final Published Versio
Los ases del toreo : Rodolfo Gaona
Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 201
Juan Belmonte
Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 201
Los ases del toreo : Juan Espinosa, Armillita
Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 201
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