120 research outputs found
Constructing a class of topological solitons in magnetohydrodynamics
We present a class of topological plasma configurations characterized by
their toroidal and poloidal winding numbers, and respectively. The
special case of and corresponds to the Kamchatnov-Hopf soliton,
a magnetic field configuration everywhere tangent to the fibers of a Hopf
fibration so that the field lines are circular, linked exactly once, and form
the surfaces of nested tori. We show that for and
these configurations represent stable, localized solutions to the
magnetohydrodynamic equations for an ideal incompressible fluid with infinite
conductivity. Furthermore, we extend our stability analysis by considering a
plasma with finite conductivity and estimate the soliton lifetime in such a
medium as a function of the toroidal winding number.Comment: 5 pages, 3 figure
Non-linear photonic crystals as a source of entangled photons
Non-linear photonic crystals can be used to provide phase-matching for
frequency conversion in optically isotropic materials. The phase-matching
mechanism proposed here is a combination of form birefringence and phase
velocity dispersion in a periodic structure. Since the phase-matching relies on
the geometry of the photonic crystal, it becomes possible to use highly
non-linear materials. This is illustrated considering a one-dimensional
periodic AlGaAs / air structure for the generation of 1.5
m light. We show that phase-matching conditions used in schemes to create
entangled photon pairs can be achieved in photonic crystals.Comment: 4 pages, 3 figure
Optimal Generation of Pulsed Entangled Photon Pairs
We experimentally investigate a double-pass parametric down-conversion scheme
for producing pulsed, polarization-entangled photon pairs with high visibility.
The amplitudes for creating photon pairs on each pass interfere to compensate
for distinguishing characteristics that normally degrade two-photon visibility.
The result is a high-flux source of polarization-entangled photon pulses that
does not require spectral filtering. We observe quantum interference visibility
of over 95% without the use of spectral filters for 200 femtosecond pulses, and
up to 98.1% with 5 nm bandwidth filters.Comment: 8 pages, 6 figure
Independent electrical tuning of separated quantum dots in coupled photonic crystal cavities
Systems of photonic crystal cavities coupled to quantum dots are a promising
architecture for quantum networking and quantum simulators. The ability to
independently tune the frequencies of laterally separated quantum dots is a
crucial component of such a scheme. Here, we demonstrate independent tuning of
laterally separated quantum dots in photonic crystal cavities coupled by
in-plane waveguides by implanting lines of protons which serve to electrically
isolate different sections of a diode structure.Comment: 3 pages, 3 figure
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