1,705 research outputs found
Quantum limits in interferometric measurements
Quantum noise limits the sensitivity of interferometric measurements. It is
generally admitted that it leads to an ultimate sensitivity, the ``standard
quantum limit''. Using a semi-classical analysis of quantum noise, we show that
a judicious use of squeezed states allows one in principle to push the
sensitivity beyond this limit. This general method could be applied to large
scale interferometers designed for gravitational wave detection.Comment: 4 page
Thermal Casimir force between nanostructured surfaces
We present detailed calculations for the Casimir force between a plane and a
nanostructured surface at finite temperature in the framework of the scattering
theory. We then study numerically the effect of finite temperature as a
function of the grating parameters and the separation distance. We also infer
non-trivial geometrical effects on the Casimir interaction via a comparison
with the proximity force approximation. Finally, we compare our calculations
with data from experiments performed with nanostructured surfaces
Radiative heat transfer between two dielectric nanogratings in the scattering approach
We present a theoretical study of radiative heat transfer between dielectric
nanogratings in the scattering approach. As a comparision with these exact
results, we also evaluate the domain of validity of Derjaguin's Proximity
Approximation (PA). We consider a system of two corrugated silica plates with
various grating geometries, separation distances, and lateral displacement of
the plates with respect to one another. Numerical computations show that while
the PA is a good approximation for aligned gratings, it cannot be used when the
gratings are laterally displaced. We illustrate this by a thermal modulator
device for nanosystems based on such a displacement
Casimir torque between corrugated metallic plates
We consider two parallel corrugated plates and show that a Casimir torque
arises when the corrugation directions are not aligned. We follow the
scattering approach and calculate the Casimir energy up to second order in the
corrugation amplitudes, taking into account nonspecular reflections,
polarization mixing and the finite conductivity of the metals. We compare our
results with the proximity force approximation, which overestimates the torque
by a factor 2 when taking the conditions that optimize the effect. We argue
that the Casimir torque could be measured for separation distances as large as
1 Comment: 7 pages, 3 figures, contribution to QFEXT07 proceeding
A practical mode system for recursive definitions
In call-by-value languages, some mutually-recursive value definitions can be
safely evaluated to build recursive functions or cyclic data structures, but
some definitions (let rec x = x + 1) contain vicious circles and their
evaluation fails at runtime. We propose a new static analysis to check the
absence of such runtime failures.
We present a set of declarative inference rules, prove its soundness with
respect to the reference source-level semantics of Nordlander, Carlsson, and
Gill (2008), and show that it can be (right-to-left) directed into an
algorithmic check in a surprisingly simple way.
Our implementation of this new check replaced the existing check used by the
OCaml programming language, a fragile syntactic/grammatical criterion which let
several subtle bugs slip through as the language kept evolving. We document
some issues that arise when advanced features of a real-world functional
language (exceptions in first-class modules, GADTs, etc.) interact with safety
checking for recursive definitions
Orbital frustration at the origin of the magnetic behavior in LiNiO2
We report on the ESR, magnetization and magnetic susceptibility measurements
performed over a large temperature range, from 1.5 to 750 K, on high-quality
stoichiometric LiNiO2. We find that this compound displays two distinct
temperature regions where its magnetic behavior is anomalous. With the help of
a statistical model based on the Kugel'-Khomskii Hamiltonian, we show that
below T_of ~ 400 K, an orbitally-frustrated state characteristic of the
triangular lattice is established. This then gives a solution to the
long-standing controversial problem of the magnetic behavior in LiNiO2.Comment: 5 pages, 5 figures, RevTex, accepted in PR
Twin polaritons in semiconductor microcavities
The quantum correlations between the beams generated by polariton pair
scattering in a semiconductor microcavity above the parametric oscillation
threshold are computed analytically. The influence of various parameters like
the cavity-exciton detuning, the intensity mismatch between the signal and
idler beams and the amount of spurious noise is analyzed. We show that very
strong quantum correlations between the signal and idler polaritons can be
achieved. The quantum effects on the outgoing light fields are strongly reduced
due to the large mismatch in the coupling of the signal and idler polaritons to
the external photons
Quantum noise in ideal operational amplifiers
We consider a model of quantum measurement built on an ideal operational
amplifier operating in the limit of infinite gain, infinite input impedance and
null output impedance and with a feddback loop. We evaluate the intensity and
voltage noises which have to be added to the classical amplification equations
in order to fulfill the requirements of quantum mechanics. We give a
description of this measurement device as a quantum network scattering quantum
fluctuations from input to output ports.Comment: 4 pages, 2 figures, RevTe
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