6,462 research outputs found
Nonclassicality of a photon-subtracted Gaussian field
Published versio
Spin Squeezing with Coherent Light via Entanglement Swapping
We analyze theoretically a scheme that produces spin squeezing via the
continuous swapping of atom-photon entanglement into atom-atom entanglement,
and propose an explicit experimental system where the necessary atom-field
coupling can be realized. This scheme is found to be robust against
perturbations due to other atom-field coupling channels.Comment: 6 pages, 10 figure
Duality Between Spatial and Angular Shift in Optical Reflection
We report a unified representation of the spatial and angular Goos-Hanchen
and Imbert-Fedorov shifts that occur when a light beam reflects from a plane
interface. We thus reveal the dual nature of spatial and angular shifts in
optical beam reflection. In the Goos-Hanchen case we show theoretically and
experimentally that this unification naturally arises in the context of
reflection from a lossy surface (e.g., a metal).Comment: 4 pages, 3 figure
Two-photon interference with two independent pseudo-thermal sources
The nature of two-photon interference is a subject that has aroused renewed
interest in recent years and is still under debate. In this paper we report the
first observation of two-photon interference with independent pseudo-thermal
sources in which sub-wavelength interference is observed. The phenomenon may be
described in terms of the classical statistical distribution of the two sources
and their optical transfer functions.Comment: Phys. Rev. A 74, 053807 (2006
Plasma interactions and surface/material effects
A discussion on plasma interactions and surface/material effects is summarized. The key issues in this area were: (1) the lack of data on the material properties of common spacecraft surface materials; (2) lack of understanding of the contamination and decontamination processes; and (3) insufficient analytical tools to model synergistic phenomena related to plasma interactions. Without an adequate database of material properties, accurate system performance predictions cannot be made. The interdisciplinary nature of the surface-plasma interactions area makes it difficult to plan and maintain a coherent theoretical and experimental program. The shuttle glow phenomenon is an excellent example of an unanticipated, complex interaction involving synergism between surface and plasma effects. Building an adequate technology base for understanding and predicting surface-plasma interactions will require the coordinated efforts of engineers, chemists, and physicists. An interdisciplinary R and D program should be organized to deal with similar problems that the space systems of the 21st century may encounter
Parameter estimation on compact binary coalescences with abruptly terminating gravitational waveforms
Gravitational-wave astronomy seeks to extract information about astrophysical
systems from the gravitational-wave signals they emit. For coalescing
compact-binary sources this requires accurate model templates for the inspiral
and, potentially, the subsequent merger and ringdown. Models with
frequency-domain waveforms that terminate abruptly in the sensitive band of the
detector are often used for parameter-estimation studies. We show that the
abrupt waveform termination contains significant information that affects
parameter-estimation accuracy. If the sharp cutoff is not physically motivated,
this extra information can lead to misleadingly good accuracy claims. We also
show that using waveforms with a cutoff as templates to recover complete
signals can lead to biases in parameter estimates. We evaluate when the
information content in the cutoff is likely to be important in both cases. We
also point out that the standard Fisher matrix formalism, frequently employed
for approximately predicting parameter-estimation accuracy, cannot properly
incorporate an abrupt cutoff that is present in both signals and templates;
this observation explains some previously unexpected results found in the
literature. These effects emphasize the importance of using complete waveforms
with accurate merger and ringdown phases for parameter estimation.Comment: Very minor changes to match published versio
Decoherence of Quantum-Enhanced Timing Accuracy
Quantum enhancement of optical pulse timing accuracy is investigated in the
Heisenberg picture. Effects of optical loss, group-velocity dispersion, and
Kerr nonlinearity on the position and momentum of an optical pulse are studied
via Heisenberg equations of motion. Using the developed formalism, the impact
of decoherence by optical loss on the use of adiabatic soliton control for
beating the timing standard quantum limit [Tsang, Phys. Rev. Lett. 97, 023902
(2006)] is analyzed theoretically and numerically. The analysis shows that an
appreciable enhancement can be achieved using current technology, despite an
increase in timing jitter mainly due to the Gordon-Haus effect. The decoherence
effect of optical loss on the transmission of quantum-enhanced timing
information is also studied, in order to identify situations in which the
enhancement is able to survive.Comment: 12 pages, 4 figures, submitte
Coherent properties of nano-electromechanical systems
We study the properties of a nano-electromechanical system in the coherent
regime, where the electronic and vibrational time scales are of the same order.
Employing a master equation approach, we obtain the stationary reduced density
matrix retaining the coherences between vibrational states. Depending on the
system parameters, two regimes are identified, characterized by either () an
{\em effective} thermal state with a temperature {\em lower} than that of the
environment or () strong coherent effects. A marked cooling of the
vibrational degree of freedom is observed with a suppression of the vibron Fano
factor down to sub-Poissonian values and a reduction of the position and
momentum quadratures.Comment: 12 pages, 11 figure
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