11,849 research outputs found
Parametric generation of quadrature squeezing of mirrors in cavity optomechanics
We propose a method to generate quadrature squeezed states of a moving mirror
in a Fabry-Perot cavity. This is achieved by exploiting the fact that when the
cavity is driven by an external field with a large detuning, the moving mirror
behaves as a parametric oscillator. We show that parametric resonance can be
reached approximately by modulating the driving field amplitude at a frequency
matching the frequency shift of the mirror. The parametric resonance leads to
an efficient generation of squeezing, which is limited by the thermal noise of
the environment.Comment: 4 pages, 2 figure
Correlated two-photon transport in a one-dimensional waveguide side-coupled to a nonlinear cavity
We investigate the transport properties of two photons inside a
one-dimensional waveguide side-coupled to a single-mode nonlinear cavity. The
cavity is filled with a nonlinear Kerr medium. Based on the Laplace transform
method, we present analytic solution of quantum states of the transmitted and
reflected two photons, which are initially prepared in a Lorentzian wave
packet. The solution reveals how quantum correlation between the two photons
emerge after the scattering by the nonlinear cavity. In particular, we show
that the output wave function of the two photons in position space can be
localized in the relative coordinates, which is a feature that may be
interpreted as a two-photon bound state in this waveguide-cavity system.Comment: 9 pages, 5 figure
Spectrum of single-photon emission and scattering in cavity optomechanics
We present an analytic solution describing the quantum state of a single
photon after interacting with a moving mirror in a cavity. This includes
situations when the photon is initially stored in a cavity mode as well as when
the photon is injected into the cavity. In addition, we obtain the spectrum of
the output photon in the resolved-sideband limit, which reveals spectral
features of the single-photon strong-coupling regime in this system. We also
clarify the conditions under which the phonon sidebands are visible and the
photon-state frequency shift can be resolved.Comment: 5 pages, 5 figure
Exclusive J/\psi Productions at e^+ e^- Colliders
Exclusive quarkonium pair production in electron-positron collisions is
studied in non-relativistic QCD. The obtained cross section for J/\psi + \eta_c
production in the leading order is confronted against the recent measurements
by the Belle Collaboration at KEKB. It is shown that a large renormalization
K-factor is necessary to explain the experimental data. We point out that the
J^{PC}=0^{-+} nature of the hadronic systems that are assigned to be \eta_c
should be tested by the triple angular distributions in terms of the scattering
angle, and, polar and azimuthal angles of J/\psi into leptons. We further study
J/\psi + J/\psi and \Upsilon + \Upsilon productions at LEP energies. Although
the axial-vector couplings of the Z-boson to charm and bottom quarks allow
production of such pairs when one of them is polarised transversally and the
other longitudinally, we find that the integrated luminosity at Z pole
accumulated by LEP is not large enough to observe the exclusive pair production
of quarkonium.Comment: 11 pages, 2 eps figures, LaTe
Structural Phases of Bounded Three-Dimensional Screened Coulomb Clusters (Finite Yukawa System)
The formation of three-dimensional (3D) dust clusters within a complex plasma
modeled as a spatially confined Yukawa system is simulated using the box_tree
code. Similar to unscreened Coulomb clusters, the occurrence of concentric
shells with characteristic occupation numbers was observed. Both the occupation
numbers and radii were found to depend on the Debye length. Ground and low
energy meta-stable states of the shielded 3D Coulomb clusters were determined
for 4<N<20. The structure and energy of the clusters in different states was
analyzed for various Debye lengths. Structural phase transitions, including
inter-shell structural phase transitions and intra-shell structural phase
transitions, were observed for varying Debye length and the critical value for
transitions calculated
Numerical Simulations and Analysis of Thermally Excited Waves in Plasma Crystals
A numerical model for a 2D-monolayer plasma crystal was established using the
Box_tree code. Box_tree is a Barnes_Hut tree code which has proven effective in
modeling systems composed of large numbers of particles. Thermally excited
waves in this plasma crystal were numerically simulated and dispersion
relations for both the longitudinal and transverse wave modes were found. These
were compared with the dispersion relations extrapolated from experiment as
well as a theory based on harmonic approximation. The results were found to
agree with theoretical dispersion relations under different wave propagation
directions with different particle charges and over a range of 0.9<k<5.Comment: 7 pages, Presented at COSPAR '0
Correlated two-photon scattering in cavity optomechanics
We present an exact analytical solution of the two-photon scattering in a
cavity optomechanical system. This is achieved by solving the quantum dynamics
of the total system, including the optomechanical cavity and the cavity-field
environment, with the Laplace transform method. The long-time solution reveals
detailed physical processes involved as well as the corresponding resonant
photon frequencies. We characterize the photon correlation induced in the
scattering process by calculating the two-photon joint spectrum of the
long-time state. Clear evidence for photon frequency anti-correlation can be
observed in the joint spectrum. In addition, we calculate the equal-time
second-order correlation function of the cavity photons. The results show that
the radiation pressure coupling can induce photon blockade effect, which is
strongly modulated by the phonon sideband resonance. In particular, we obtain
an explicit expression of optomechanical coupling strength determining these
sideband modulation peaks based on the two-photon resonance condition.Comment: 10 pages, 6 figure
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