3,644 research outputs found
Convergence of all-order many-body methods: coupled-cluster study for Li
We present and analyze results of the relativistic coupled-cluster
calculation of energies, hyperfine constants, and dipole matrix elements for
the , , and states of Li atom. The calculations are
complete through the fourth order of many-body perturbation theory for energies
and through the fifth order for matrix elements and subsume certain chains of
diagrams in all orders. A nearly complete many-body calculation allows us to
draw conclusions on the convergence pattern of the coupled-cluster method. Our
analysis suggests that the high-order many-body contributions to energies and
matrix elements scale proportionally and provides a quantitative ground for
semi-empirical fits of {\em ab inito} matrix elements to experimental energies.Comment: 4 pages, 3 figure
Polariton quantum blockade in a photonic dot
We investigate the quantum nonlinear dynamics of a resonantly excited
photonic quantum dot embedding a quantum well in the strong exciton-photon
coupling regime. Within a master equation approach, we study the polariton
quantum blockade and the generation of single photon states due to
polariton-polariton interactions as a function of the photonic dot geometry,
spectral linewidths and energy detuning between quantum well exciton and
confined photon mode. The second order coherence function is
calculated for both continuous wave and pulsed excitations
On-chip cavity quantum phonodynamics with an acceptor qubit in silicon
We describe a chip-based, solid-state analogue of cavity-QED utilizing
acoustic phonons instead of photons. We show how long-lived and tunable
acceptor impurity states in silicon nanomechanical cavities can play the role
of a matter non-linearity for coherent phonons just as, e.g., the Josephson
qubit plays in circuit-QED. Both strong coupling (number of Rabi oscillations ~
100) and strong dispersive coupling (0.1-2 MHz) regimes can be reached in
cavities in the 1-20 GHz range, enabling the control of single phonons,
phonon-phonon interactions, dispersive phonon readout of the acceptor qubit,
and compatibility with other optomechanical components such as phonon-photon
translators. We predict explicit experimental signatures of the acceptor-cavity
system.Comment: 6 pages, 2 figures, PDFLaTeX. New version improves clarit
Light scattering from ultracold atoms in optical lattices as an optical probe of quantum statistics
We study off-resonant collective light scattering from ultracold atoms
trapped in an optical lattice. Scattering from different atomic quantum states
creates different quantum states of the scattered light, which can be
distinguished by measurements of the spatial intensity distribution, quadrature
variances, photon statistics, or spectral measurements. In particular,
angle-resolved intensity measurements reflect global statistics of atoms (total
number of radiating atoms) as well as local statistical quantities (single-site
statistics even without an optical access to a single site) and pair
correlations between different sites. As a striking example we consider
scattering from transversally illuminated atoms into an optical cavity mode.
For the Mott insulator state, similar to classical diffraction, the number of
photons scattered into a cavity is zero due to destructive interference, while
for the superfluid state it is nonzero and proportional to the number of atoms.
Moreover, we demonstrate that light scattering into a standing-wave cavity has
a nontrivial angle dependence, including the appearance of narrow features at
angles, where classical diffraction predicts zero. The measurement procedure
corresponds to the quantum non-demolition (QND) measurement of various atomic
variables by observing light.Comment: 15 pages, 5 figure
Cooling and squeezing via quadratic optomechanical coupling
We explore the physics of optomechanical systems in which an optical cavity
mode is coupled parametrically to the square of the position of a mechanical
oscillator. We derive an effective master equation describing two-phonon
cooling of the mechanical oscillator. We show that for high temperatures and
weak coupling, the steady-state phonon number distribution is non-thermal
(Gaussian) and that even for strong cooling the mean phonon number remains
finite. Moreover, we demonstrate how to achieve mechanical squeezing by driving
the cavity with two beams. Finally, we calculate the optical output and
squeezing spectra. Implications for optomechanics experiments with the
membrane-in-the-middle geometry or ultracold atoms in optical resonators are
discussed.Comment: 4 pages, 3 figure
Dynamical Casimir Effect in Optically Modulated Cavities
Cavities with periodically oscillating mirrors have been predicted to excite
photon pairs out of the quantum vacuum in a process known as the Dynamical
Casimir effect. Here we propose and analyse an experimental layout that can
provide an efficient modulation of the effective optical length of a cavity
mode in the near-infrared spectral region. An analytical model of the dynamical
Casimir emission is developed and compared to the predictions of a direct
numerical solution of Maxwell's equations in real time. A sizeable intensity of
dynamical Casimir emission is anticipated for realistic operating parameters.
In the presence of an external coherent seed beam, we predict amplification of
the seed beam and the appearance of an additional phase-conjugate beam as a
consequence of stimulated dynamical Casimir processes.Comment: 6 pages, 5 figure
Detecting phonons and persistent currents in toroidal Bose-Einstein condensates by means of pattern formation
We theoretically investigate the dynamic properties of a Bose-Einstein
condensate in a toroidal trap. A periodic modulation of the transverse
confinement is shown to produce a density pattern due to parametric
amplification of phonon pairs. By imaging the density distribution after free
expansion one obtains i) a precise determination of the Bogoliubov spectrum and
ii) a sensitive detection of quantized circulation in the torus. The parametric
amplification is also sensitive to thermal and quantum fluctuations.Comment: 4 pages, 4 figures; new figures, revised version to appear as a Rapid
Communication in Physical Review
Quantum Monte Carlo study of ring-shaped polariton parametric luminescence in a semiconductor microcavity
We present a quantum Monte Carlo study of the quantum correlations in the
parametric luminescence from semiconductor microcavities in the strong
exciton-photon coupling regime. As already demonstrated in recent experiments,
a ring-shaped emission is obtained by applying two identical pump beams with
opposite in-plane wavevectors, providing symmetrical signal and idler beams
with opposite in-plane wavevectors on the ring. We study the squeezing of the
signal-idler difference noise across the parametric instability threshold,
accounting for the radiative and non-radiative losses, multiple scattering and
static disorder. We compare the results of the complete multimode Monte Carlo
simulations with a simplified linearized quantum Langevin analytical model
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