323 research outputs found
Opto-mechanical micro-macro entanglement
We propose to create and detect opto-mechanical entanglement by storing one
component of an entangled state of light in a mechanical resonator and then
retrieving it. Using micro-macro entanglement of light as recently demonstrated
experimentally, one can then create opto-mechanical entangled states where the
components of the superposition are macroscopically different. We apply this
general approach to two-mode squeezed states where one mode has undergone a
large displacement. Based on an analysis of the relevant experimental
imperfections, the scheme appears feasible with current technology.Comment: 7 pages, 6 figures, to appear in PRL, submission coordinated with
Sekatski et al. who reported on similar result
Antenna Design for Ultra Wideband Application Using Stacked Multiresonator Patches
As wireless communication applications require more and more bandwidth, the demand for wideband antennas increases as well. For instance, the ultra wideband radio (UWB) utilizes the frequency band of 3.1-10.6 GHz .This paper presents some of the work carried out within ULTRAWAVES in the area of antenna design and analysis. Two antennas have been designed, optimized and simulated using Stacked Multiresonator patches. In addition results and conclusions are presente
A Comparative Study of Different Phase Detrending Algorithms for Scintillation Monitoring
Rapid and sudden fluctuations of phase and amplitude in Global Navigation Satellite System (GNSS) signals due to diffraction of the ionosphere phase components when signals passing through small-scale irregularities (less than hundreds meters) are commonly so-called ionospheric scintillation. The aim of the paper is to analyze the implementation and compare the performance of different phase detrending algorithms to improve scintillation monitoring. Three different phase detrending methods, namely, three cascaded second-order high pass filters, six order Butterworth filter conducted by cascading six first-order high pass Butterworth filters, and Fast Iterative Filter (FIF) are considered in this paper. The study exploits real GNSS signals (GPS L1, Galileo E1b) affected by significant phase scintillation effects, collected in early September 2017 at Brazilian Centro de Radioastronomia e Astrofisica Mackenzie (CRAAM) monitoring station and at Adventdalen (Svalbard, Norway) research station. In this study, a software defined radio (SDR) based GNSS receiver is used to process GNSS signals and to implement the aforementioned detrending algorithms
Optomechanical Entanglement in the Presence of Laser Phase Noise
We study the simplest optomechanical system in the presence of laser phase
noise using the covariance matrix formalism. We show that the destructive
effect of the phase noise is especially strong in the bistable regime. This
explains why ground state cooling is still possible in the presence of phase
noise, as it happens far away from the bistable regime. On the other hand, the
optomechanical entanglement is strongly affected by phase noise.Comment: 5 pages, 3 figure
Macroscopic superpositions via nested interferometry: finite temperature and decoherence considerations
Recently there has been much interest in optomechanical devices for the
production of macroscopic quantum states. Here we focus on a proposed scheme
for achieving macroscopic superpositions via nested interferometry. We consider
the effects of finite temperature on the superposition produced. We also
investigate in detail the scheme's feasibility for probing various novel
decoherence mechanisms.Comment: 12 pages, 2 figure
Dynamics of levitated nanospheres: towards the strong coupling regime
The use of levitated nanospheres represents a new paradigm for the
optomechanical cooling of a small mechanical oscillator, with the prospect of
realising quantum oscillators with unprecedentedly high quality factors. We
investigate the dynamics of this system, especially in the so-called
self-trapping regimes, where one or more optical fields simultaneously trap and
cool the mechanical oscillator. The determining characteristic of this regime
is that both the mechanical frequency and single-photon
optomechanical coupling strength parameters are a function of the optical
field intensities, in contrast to usual set-ups where and are
constant for the given system. We also measure the characteristic transverse
and axial trapping frequencies of different sized silica nanospheres in a
simple optical standing wave potential, for spheres of radii \,nm,
illustrating a protocol for loading single nanospheres into a standing wave
optical trap that would be formed by an optical cavity. We use this data to
confirm the dependence of the effective optomechanical coupling strength on
sphere radius for levitated nanospheres in an optical cavity and discuss the
prospects for reaching regimes of strong light-matter coupling. Theoretical
semiclassical and quantum displacement noise spectra show that for larger
nanospheres with \,nm a range of interesting and novel dynamical
regimes can be accessed. These include simultaneous hybridization of the two
optical modes with the mechanical modes and parameter regimes where the system
is bistable. We show that here, in contrast to typical single-optical mode
optomechanical systems, bistabilities are independent of intracavity intensity
and can occur for very weak laser driving amplitudes
Adaptive Phase Detrending for GNSS Scintillation Detection: A Case Study Over Antarctica
We aim at contributing to the reliability of the phase scintillation index on Global Navigation Satellite System (GNSS) signals at high-latitude. To the scope, we leverage on a recently introduced detrending scheme based on the signal decomposition provided by the fast iterative filtering (FIF) technique. This detrending scheme has been demonstrated to enable a fine-tuning of the cutoff frequency for phase detrending used in the phase scintillation index definition. In a single case study based on Galileo data taken by a GNSS ionospheric scintillation monitor receiver (ISMR) in Concordia Station (Antarctica), we investigate how to step ahead of the cutoff frequency optimization. We show how the FIF-based detrending allows deriving adaptive cutoff frequencies, whose value changes minute-by-minute. They are found to range between 0.4 and 1.2 Hz. This allows better accounting for diffractive effects in phase scintillation index calculation and provides a GNSS-based estimation of the relative velocity between satellite and ionospheric irregularities
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