194 research outputs found
Dipole lasing phase transitions in media with singularities in polarizabilities
We show that a divergence in the optical polarizability of a heterogeneous medium with nonlinear amplification and a strong dipole-dipole interaction between particles can lead to a phase transition, for which the dipole momentum of the particles or the dipole radiation rate can be taken as order parameters. The "dipole laser" (Phys. Rev. A 71, 063812 (2005)) can be used both as a simple example of such a second-order phase transition and to provide a recipe for its analysis. We show that similar phase transitions may be possible for a nanoparticle on the surface of an optically active medium and at the "Clausius-Mossotti" catastrophe in a bulk heterogeneous medium
Conditional quantum logic using two atomic qubits
In this paper we propose and analyze a feasible scheme where the detection of
a single scattered photon from two trapped atoms or ions performs a conditional
unitary operation on two qubits. As examples we consider the preparation of all
four Bell states, the reverse operation that is a Bell measurement, and a CNOT
gate. We study the effect of atomic motion and multiple scattering, by
evaluating Bell inequalities violations, and by calculating the CNOT gate
fidelity.Comment: 23 pages, 8 figures in 11 file
Dipole Response of Spaser on an External Optical Wave
We find the conditions upon the amplitude and frequency of an external
electromagnetic field at which the dipole moment of a Bergman-Stockman spaser
oscillates in antiphase with the field. For these values of the amplitude and
frequency the losses in metal nanoparticles is exactly compensated of by gain.
This shows that spasers may be used as inclusions in designing lossless
metamaterials
Dipole nanolaser
A "dipole" laser is proposed consisting of a nanoparticle and a two-level system with population inversion. If the threshold conditions are fulfilled, the dipole interaction between the two-level system and the nanoparticle leads to coherent oscillations in the polarization of the particles, even in the absence of an external electromagnetic field. The emitted radiation has a dipolar distribution. It does not need an optical cavity, and has a very small volume, 0.1 mu m(3), which can be important for applications in microelectronics. Estimates of the threshold conditions are carried out for a dipole laser composed of a quantum dot and a silver nanoparticle
The influence of co additive on the sintering, mechanical properties, cytocompatibility, and digital light processing based stereolithography of 3y-tzp-5al2 o3 ceramics
Nanocrystalline 3 mol% yttria-tetragonal zirconia polycrystal (3Y-TZP) ceramic powder containing 5 wt. % Al2 O3 with 64 m2 /g specific area was synthesized through precipitation method. The developed materials and technology could be the basis for 3D manufacturing of bioceramic implants for medicin
The influence of co additive on the sintering, mechanical properties, cytocompatibility, and digital light processing based stereolithography of 3Y-TZP-5Al₂O₃ ceramics
Nanocrystalline 3 mol% yttria-tetragonal zirconia polycrystal (3Y-TZP) ceramic powder containing 5 wt. % Al₂O₃ with 64 m²/g specific area was synthesized through precipitation method. Diferent amounts of Co (0-3 mol%) were introduced into synthesized powders, and ceramic materials were obtained by heat treatment in the air for 2 h at 1350-1550 °
Internal photoemission from plasmonic nanoparticles: comparison between surface and volume photoelectric effects
We study emission of photoelectrons from plasmonic nanoparticles into
surrounding matrix. We consider two mechanisms of the photoelectric effect from
nanoparticles - surface and volume ones, and use models of these two effects
which allow us to obtain analytical results for the photoelectron emission
rates from nanoparticle. Calculations have been done for the step potential at
surface of spherical nanoparticle, and the simple model for the hot electron
cooling have been used. We highlight the effect of the discontinuity of the
dielectric permittivity at the nanoparticle boundary in the surface mechanism,
which leads to substantial (by 5 times) increase of photoelectron emission rate
from nanoparticle compared to the case when such discontinuity is absent. For
plasmonic nanoparticle, a comparison of two mechanisms of the photoeffect was
done for the first time and showed that surface photoeffect, at least, does not
concede the volume one, which agrees with results for the flat metal surface
first formulated by Tamm and Schubin in their pioneering development of
quantum-mechanical theory of photoeffect in 1931. In accordance with our
calculations, this predominance of the surface effect is a result of effective
cooling of hot carriers, during their propagation from volume of the
nanoparticle to its surface in the scenario of the volume mechanism. Taking
into account both mechanisms is essential in development of devices based on
the photoelectric effect and in usage of hot electrons from plasmonic
nanoantenna.Comment: 13 pages, 10 figures, 61 reference
Photon polarisation entanglement from distant dipole sources
It is commonly believed that photon polarisation entanglement can only be
obtained via pair creation within the same source or via postselective
measurements on photons that overlapped within their coherence time inside a
linear optics setup. In contrast to this, we show here that polarisation
entanglement can also be produced by distant single photon sources in free
space and without the photons ever having to meet, if the detection of a photon
does not reveal its origin -- the which way information. In the case of two
sources, the entanglement arises under the condition of two emissions in
certain spatial directions and leaves the dipoles in a maximally entangled
state.Comment: 7 pages, 2 figures, revised version, accepted for publication in J.
Phys.
Survival of Chondrocytes in Rabbit Septal Cartilage After Electromechanical Reshaping
Electromechanical reshaping (EMR) has been recently described as an alternative method for reshaping facial cartilage without the need for incisions or sutures. This study focuses on determining the short- and long-term viability of chondrocytes following EMR in cartilage grafts maintained in tissue culture. Flat rabbit nasal septal cartilage specimens were bent into semi-cylindrical shapes by an aluminum jig while a constant electric voltage was applied across the concave and convex surfaces. After EMR, specimens were maintained in culture media for 64 days. Over this time period, specimens were serially biopsied and then stained with a fluorescent live–dead assay system and imaged using laser scanning confocal microscopy. In addition, the fraction of viable chondrocytes was measured, correlated with voltage, voltage application time, electric field configuration, and examined serially. The fraction of viable chondrocytes decreased with voltage and application time. High local electric field intensity and proximity to the positive electrode also focally reduced chondrocyte viability. The density of viable chondrocytes decreased over time and reached a steady state after 2–4 weeks. Viable cells were concentrated within the central region of the specimen. Approximately 20% of original chondrocytes remained viable after reshaping with optimal voltage and application time parameters and compared favorably with conventional surgical shape change techniques such as morselization
Optimizing the fast Rydberg quantum gate
The fast phase gate scheme, in which the qubits are atoms confined in sites
of an optical lattice, and gate operations are mediated by excitation of
Rydberg states, was proposed by Jaksch et al. Phys. Rev. Lett. 85, 2208 (2000).
A potential source of decoherence in this system derives from motional heating,
which occurs if the ground and Rydberg states of the atom move in different
optical lattice potentials. We propose to minimize this effect by choosing the
lattice photon frequency \omega so that the ground and Rydberg states have the
same frequency-dependent polarizability \alpha(omega). The results are
presented for the case of Rb.Comment: 5 pages, submitted to PR
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