12,163 research outputs found
Helical Structures in Vertically Aligned Dust Particle Chains in a Complex Plasma
Self-assembly of structures from vertically aligned, charged dust particle
bundles within a glass box placed on the lower, powered electrode of a RF GEC
cell were produced and examined experimentally. Self-organized formation of
one-dimensional vertical chains, two-dimensional zigzag structures and
three-dimensional helical structures of triangular, quadrangular, pentagonal,
hexagonal, and heptagonal symmetries are shown to occur. System evolution is
shown to progress from a one-dimensional chain structure, through a zigzag
transition to a two-dimensional, spindle-like structure and then to various
three-dimensional, helical structures exhibiting multiple symmetries. Stable
configurations are found to be dependent upon the system confinement, (where
are the horizontal and vertical dust resonance frequencies), the total number
of particles within a bundle and the RF power. For clusters having fixed
numbers of particles, the RF power at which structural transitions occur is
repeatable and exhibits no observable hysteresis. The critical conditions for
these structural transitions as well as the basic symmetry exhibited by the
one-, two- and three-dimensional structures that subsequently develop are in
good agreement with the theoretically predicted configurations of minimum
energy determined employing molecular dynamics simulations for charged dust
particles confined in a prolate, spheroidal potential as presented
theoretically by Kamimura and Ishihara [10]
Entanglement fidelity and measurement of entanglement preserving in quantum processes
The entanglement fidelity provides a measure of how well the entanglement
between two subsystems is preserved in a quantum process. By using a simple
model we show that in some cases this quantity in its original definition fails
in the measurement of the entanglement preserving. On the contrary, the
modified entanglement fidelity, obtained by using a proper local unitary
transformation on a subsystem, is shown to exhibit the behavior similar to that
of the concurrence in the quantum evolution.Comment: 4 pages, 2 figures. v2: repaired a severe oversight, removed an
incorrect claim, added references; v3: version accepted for publication in
Phys. Rev.
Realizing quantum controlled phase-flip gate through quantum dot in silicon slow-light photonic crystal waveguide
We propose a scheme to realize controlled phase gate between two single
photons through a single quantum dot in slow-light silicon photonic crystal
waveguide. Enhanced Purcell factor and beta factor lead to high gate fidelity
over broadband frequencies compared to cavity-assisted system. The excellent
physical integration of this silicon photonic crystal waveguide system provides
tremendous potential for large-scale quantum information processing.Comment: 9 pages, 3 figure
Simultaneous Measurements of Microwave Photoresistance and Cyclotron Reflection in the Multi-Photon Regime
We simultaneously measure photoresistance with electrical transport and
plasmon-cyclotron resonance (PCR) using microwave reflection spectroscopy in
high mobility GaAs/AlGaAs quantum wells under a perpendicular magnetic field.
Multi-photon transitions are revealed as sharp peaks in the resistance and the
cyclotron reflection on samples with various carrier densities. Our main
finding is that plasmon coupling is relevant in the cyclotron reflection
spectrum but has not been observed in the electrical conductivity signal. We
discuss possible mechanisms relevant to reflection or dc conductivity signal to
explain this discrepancy. We further confirm a trend that higher order
multi-photon features can be observed using higher carrier density samples.Comment: 19 pages, 5 figure
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