126 research outputs found
Grasp planning under uncertainty
The planning of dexterous grasps for multifingered robot hands operating in uncertain environments is covered. A sensor-based approach to the planning of a reach path prior to grasping is first described. An on-line, joint space finger path planning algorithm for the enclose phase of grasping was then developed. The algorithm minimizes the impact momentum of the hand. It uses a Preshape Jacobian matrix to map task-level hand preshape requirements into kinematic constraints. A master slave scheme avoids inter-finger collisions and reduces the dimensionality of the planning problem
Signal-to-noise ratio of Gaussian-state ghost imaging
The signal-to-noise ratios (SNRs) of three Gaussian-state ghost imaging
configurations--distinguished by the nature of their light sources--are
derived. Two use classical-state light, specifically a joint signal-reference
field state that has either the maximum phase-insensitive or the maximum
phase-sensitive cross correlation consistent with having a proper
representation. The third uses nonclassical light, in particular an entangled
signal-reference field state with the maximum phase-sensitive cross correlation
permitted by quantum mechanics. Analytic SNR expressions are developed for the
near-field and far-field regimes, within which simple asymptotic approximations
are presented for low-brightness and high-brightness sources. A high-brightness
thermal-state (classical phase-insensitive state) source will typically achieve
a higher SNR than a biphoton-state (low-brightness, low-flux limit of the
entangled-state) source, when all other system parameters are equal for the two
systems. With high efficiency photon-number resolving detectors, a
low-brightness, high-flux entangled-state source may achieve a higher SNR than
that obtained with a high-brightness thermal-state source.Comment: 12 pages, 4 figures. This version incorporates additional references
and a new analysis of the nonclassical case that, for the first time,
includes the complete transition to the classical signal-to-noise ratio
asymptote at high source brightnes
Classical capacity of bosonic broadcast communication and a new minimum output entropy conjecture
Previous work on the classical information capacities of bosonic channels has
established the capacity of the single-user pure-loss channel, bounded the
capacity of the single-user thermal-noise channel, and bounded the capacity
region of the multiple-access channel. The latter is a multi-user scenario in
which several transmitters seek to simultaneously and independently communicate
to a single receiver. We study the capacity region of the bosonic broadcast
channel, in which a single transmitter seeks to simultaneously and
independently communicate to two different receivers. It is known that the
tightest available lower bound on the capacity of the single-user thermal-noise
channel is that channel's capacity if, as conjectured, the minimum von Neumann
entropy at the output of a bosonic channel with additive thermal noise occurs
for coherent-state inputs. Evidence in support of this minimum output entropy
conjecture has been accumulated, but a rigorous proof has not been obtained. In
this paper, we propose a new minimum output entropy conjecture that, if proved
to be correct, will establish that the capacity region of the bosonic broadcast
channel equals the inner bound achieved using a coherent-state encoding and
optimum detection. We provide some evidence that supports this new conjecture,
but again a full proof is not available.Comment: 13 pages, 7 figure
Extracting Spatial Information from Noise Measurements of Multi-Spatial-Mode Quantum States
We show that it is possible to use the spatial quantum correlations present
in twin beams to extract information about the shape of a mask in the path of
one of the beams. The scheme, based on noise measurements through homodyne
detection, is useful in the regime where the number of photons is low enough
that direct detection with a photodiode is difficult but high enough that
photon counting is not an option. We find that under some conditions the use of
quantum states of light leads to an enhancement of the sensitivity in the
estimation of the shape of the mask over what can be achieved with a classical
state with equivalent properties (mean photon flux and noise properties). In
addition, we show that the level of enhancement that is obtained is a result of
the quantum correlations and cannot be explained with only classical
correlations
Quantum-inspired interferometry with chirped laser pulses
We introduce and implement an interferometric technique based on chirped
femtosecond laser pulses and nonlinear optics. The interference manifests as a
high-visibility (> 85%) phase-insensitive dip in the intensity of an optical
beam when the two interferometer arms are equal to within the coherence length
of the light. This signature is unique in classical interferometry, but is a
direct analogue to Hong-Ou-Mandel quantum interference. Our technique exhibits
all the metrological advantages of the quantum interferometer, but with signals
at least 10^7 times greater. In particular we demonstrate enhanced resolution,
robustness against loss, and automatic dispersion cancellation. Our
interferometer offers significant advantages over previous technologies, both
quantum and classical, in precision time delay measurements and biomedical
imaging.Comment: 6 pages, 4 figure
Inactivation of Staphylococcus aureus in raw salmon with supercritical CO2 using experimental design
All-depth dispersion cancellation in spectral domain optical coherence tomography using numerical intensity correlations
In ultra-high resolution (UHR-) optical coherence tomography (OCT) group velocity dispersion (GVD) must be corrected for in order to approach the theoretical resolution limit. One approach promises not only compensation, but complete annihilation of even order dispersion effects, and that at all sample depths. This approach has hitherto been demonstrated with an experimentally demanding ‘balanced detection’ configuration based on using two detectors. We demonstrate intensity correlation (IC) OCT using a conventional spectral domain (SD) UHR-OCT system with a single detector. IC-SD-OCT configurations exhibit cross term ghost images and a reduced axial range, half of that of conventional SD-OCT. We demonstrate that both shortcomings can be removed by applying a generic artefact reduction algorithm and using analytic interferograms. We show the superiority of IC-SD-OCT compared to conventional SD-OCT by showing how IC-SD-OCT is able to image spatial structures behind a strongly dispersive silicon wafer. Finally, we question the resolution enhancement of 2–? that IC-SD-OCT is often believed to have compared to SD-OCT. We show that this is simply the effect of squaring the reflectivity profile as a natural result of processing the product of two intensity spectra instead of a single spectrum
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