98 research outputs found
Generation of spatial antibunching with free propagating twin beams
We propose and implement a novel method to produce a spatial anti-bunched
field with free propagating twin beams from spontaneous parametric
down-conversion. The method consists in changing the spatial propagation by
manipulating the transverse degrees of freedom through reflections of one of
the twin beams. Our method use reflective elements eliminating losses from
absorption by the objects inserted in the beams.Comment: Submitted for publication in Phys. Rev.
Characterization of high finesse mirrors: loss, phase shifts and mode structure in an optical cavity
An extensive characterization of high finesse optical cavities used in cavity
QED experiments is described. Different techniques in the measurement of the
loss and phase shifts associated with the mirror coatings are discussed and
their agreement shown. Issues of cavity field mode structure supported by the
dielectric coatings are related to our effort to achieve the strongest possible
coupling between an atom and the cavity.Comment: 8 pages, 4 figure
Spatial antibunching of photons with parametric down-conversion
The theoretical framework behind a recent experiment by Nogueira et. al.
[Phys. Rev. Lett. 86}, 4009 (2001)] of spatial antibunching in a two-photon
state generated by collinear type II parametric down-conversion and a
birefringent double-slit is presented. The fourth-order quantum correlation
function is evaluated and shown to violate the classical Schwarz-type
inequality, ensuring that the field does not have a classical analog. We expect
these results to be useful in the rapidly growing fields of quantum imaging and
quantum information.Comment: 5 pages, 3 figures. Minor changes made, accepted for publication in
PR
Strongly focused light beams interacting with single atoms in free space
We construct 3-D solutions of Maxwell's equations that describe Gaussian
light beams focused by a strong lens. We investigate the interaction of such
beams with single atoms in free space and the interplay between angular and
quantum properties of the scattered radiation. We compare the exact results
with those obtained with paraxial light beams and from a standard input-output
formalism. We put our results in the context of quantum information processing
with single atoms.Comment: 9 pages, 9 figure
Optimal Sizes of Dielectric Microspheres for Cavity QED with Strong Coupling
The whispering gallery modes (WGMs) of quartz microspheres are investigated
for the purpose of strong coupling between single photons and atoms in cavity
quantum electrodynamics (cavity QED). Within our current understanding of the
loss mechanisms of the WGMs, the saturation photon number, n, and critical atom
number, N, cannot be minimized simultaneously, so that an "optimal" sphere size
is taken to be the radius for which the geometric mean, (n x N)^(1/2), is
minimized. While a general treatment is given for the dimensionless parameters
used to characterize the atom-cavity system, detailed consideration is given to
the D2 transition in atomic Cesium (852nm) using fused-silica microspheres, for
which the maximum coupling coefficient g/(2*pi)=750MHz occurs for a sphere
radius a=3.63microns corresponding to the minimum for n=6.06x10^(-6). By
contrast, the minimum for N=9.00x10^(-6) occurs for a sphere radius of
a=8.12microns, while the optimal sphere size for which (n x N)^(1/2) is
minimized occurs at a=7.83microns. On an experimental front, we have fabricated
fused-silica microspheres with radii a=10microns and consistently observed
quality factors Q=0.8x10^(7). These results for the WGMs are compared with
corresponding parameters achieved in Fabry-Perot cavities to demonstrate the
significant potential of microspheres as a tool for cavity QED with strong
coupling.Comment: 12 pages, 14 figure
Optical cavities as amplitude filters for squeezed fields
We explore the use of Fabry-P\'erot cavities as high-pass filters for
squeezed light, and show that they can increase the sensitivity of
interferometric gravitational-wave detectors without the need for long
(kilometer scale) filter cavities. We derive the parameters for the filters,
and analyze the performance of several possible cavity configurations in the
context of a future gravitational-wave interferometer with squeezed light
(vacuum) injected into the output port.Comment: 9 pages, 6 figure
New Photodetection Method Using Unbalanced Sidebands for Squeezed Quantum Noise in Gravitational Wave Interferometer
Homodyne detection is one of the ways to circumvent the standard quantum
limit for a gravitational wave detector. In this paper it will be shown that
the same quantum-non-demolition effect using homodyne detection can be realized
by heterodyne detection with unbalanced RF sidebands. Furthermore, a broadband
quantum-non-demolition readout scheme can also be realized by the unbalanced
sideband detection.Comment: 9 pages, 5 figure
Sensitivity limitations in optical speed meter topology of gravitational-wave antennae
The possible design of QND gravitational-wave detector based on speed meter
principle is considered with respect to optical losses. The detailed analysis
of speed meter interferometer is performed and the ultimate sensitivity that
can be achieved is calculated. It is shown that unlike the position meter
signal-recycling can hardly be implemented in speed meter topology to replace
the arm cavities as it is done in signal-recycled detectors, such as GEO 600.
It is also shown that speed meter can beat the Standard Quantum Limit (SQL) by
the factor of in relatively wide frequency band, and by the factor of
in narrow band. For wide band detection speed meter requires quite
reasonable amount of circulating power MW. The advantage of the
considered scheme is that it can be implemented with minimal changes in the
current optical layout of LIGO interferometer.Comment: 20 pages, 12 figure
Dynamic generation of maximally entangled photon multiplets by adiabatic passage
The adiabatic passage scheme for quantum state synthesis, in which atomic
Zeeman coherences are mapped to photon states in an optical cavity, is extended
to the general case of two degenerate cavity modes with orthogonal
polarization. Analytical calculations of the dressed-state structure and Monte
Carlo wave-function simulations of the system dynamics show that, for a
suitably chosen cavity detuning, it is possible to generate states of photon
multiplets that are maximally entangled in polarization. These states display
nonclassical correlations of the type described by Greenberger, Horne, and
Zeilinger (GHZ). An experimental scheme to realize a GHZ measurement using
coincidence detection of the photons escaping from the cavity is proposed. The
correlations are found to originate in the dynamics of the adiabatic passage
and persist even if cavity decay and GHZ state synthesis compete on the same
time scale. Beyond entangled field states, it is also possible to generate
entanglement between photons and the atom by using a different atomic
transition and initial Zeeman state.Comment: 22 pages (RevTeX), including 23 postscript figures. To be published
in Physical Review
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