644 research outputs found
Revisiting the Hanbury Brown-Twiss set-up for fractional statistics
The Hanbury Brown-Twiss experiment has proved to be an effective means of
probing statistics of particles. Here, in a set-up involving edge-state
quasiparticles in a fractional quantum Hall system, we show that a variant of
the experiment composed of two sources and two sinks can be used to unearth
fractional statistics. We find a clear cut signature of the statistics in the
equal-time current-current correlation function for quasiparticle currents
emerging from the two sources and collected at the sinks.Comment: 4 pages, 3 figure
Exploring Lifetime Effects in Femtoscopy
We investigate the role of lifetime effects from resonances and emission
duration tails in femtoscopy at RHIC in two Blast-Wave models. We find the
non-Gaussian components compare well with published source imaged data, but the
value of R_out obtained from Gaussian fits is not insensitive to the
non-Gaussian contributions when realistic acceptance cuts are applied to
models.Comment: 5 pages, 2 figure
Transition from antibunching to bunching in cavity QED
The photon statistics of the light emitted from an atomic ensemble into a
single field mode of an optical cavity is investigated as a function of the
number of atoms. The light is produced in a Raman transition driven by a pump
laser and the cavity vacuum [M.Hennrich et al., Phys. Rev. Lett. 85, 4672
(2000)], and a recycling laser is employed to repeat this process continuously.
For weak driving, a smooth transition from antibunching to bunching is found
for about one intra-cavity atom. Remarkably, the bunching peak develops within
the antibunching dip. For saturated driving and a growing number of atoms, the
bunching amplitude decreases and the bunching duration increases, indicating
the onset of Raman lasing.Comment: 4 pages, 4 figure
Investigating people: a qualitative analysis of the search behaviours of open-source intelligence analysts
The Internet and the World Wide Web have become integral parts of the lives of many modern individuals, enabling almost instantaneous communication, sharing and broadcasting of thoughts, feelings and opinions. Much of this information is publicly facing, and as such, it can be utilised in a multitude of online investigations, ranging from employee vetting and credit checking to counter-terrorism and fraud prevention/detection. However, the search needs and behaviours of these investigators are not well documented in the literature. In order to address this gap, an in-depth qualitative study was carried out in cooperation with a leading investigation company. The research contribution is an initial identification of Open-Source Intelligence investigator search behaviours, the procedures and practices that they undertake, along with an overview of the difficulties and challenges that they encounter as part of their domain. This lays the foundation for future research in to the varied domain of Open-Source Intelligence gathering
Instrumental and Analytic Methods for Bolometric Polarimetry
We discuss instrumental and analytic methods that have been developed for the
first generation of bolometric cosmic microwave background (CMB) polarimeters.
The design, characterization, and analysis of data obtained using Polarization
Sensitive Bolometers (PSBs) are described in detail. This is followed by a
brief study of the effect of various polarization modulation techniques on the
recovery of sky polarization from scanning polarimeter data. Having been
successfully implemented on the sub-orbital Boomerang experiment, PSBs are
currently operational in two terrestrial CMB polarization experiments (QUaD and
the Robinson Telescope). We investigate two approaches to the analysis of data
from these experiments, using realistic simulations of time ordered data to
illustrate the impact of instrumental effects on the fidelity of the recovered
polarization signal. We find that the analysis of difference time streams takes
full advantage of the high degree of common mode rejection afforded by the PSB
design. In addition to the observational efforts currently underway, this
discussion is directly applicable to the PSBs that constitute the polarized
capability of the Planck HFI instrument.Comment: 23 pages, 11 figures. for submission to A&
Small size boundary effects on two-pion interferometry
The Bose-Einstein correlations of two identically charged pions are derived
when these particles, the most abundantly produced in relativistic heavy ion
collisions, are confined in finite volumes. Boundary effects on single pion
spectrum are also studied. Numerical results emphasize that conventional
formulation usually adopted to describe two-pion interferometry should not be
used when the source size is small, since this is the most sensitive case to
boundary effects. Specific examples are considered for better illustration.Comment: more discussion on Figure4 and diffuse boundar
Quantum multimode model of elastic scattering from Bose Einstein condensates
Mean field approximation treats only coherent aspects of the evolution of a
Bose Einstein condensate. However, in many experiments some atoms scatter out
of the condensate. We study an analytic model of two counter-propagating atomic
Gaussian wavepackets incorporating dynamics of incoherent scattering processes.
Within the model we can treat processes of elastic collision of atoms into the
initially empty modes, and observe how, with growing occupation, the bosonic
enhancement is slowly kicking in. A condition for bosonic enhancement effect is
found in terms of relevant parameters. Scattered atoms form a squeezed state
that can be viewed as a multi-component condensate. Not only are we able to
calculate the dynamics of mode occupation, but also the full statistics of
scattered atoms.Comment: 4 pages, 4 figure
Witnessing Entanglement of EPR States With Second-Order Interference
The separability of the continuous-variable EPR state can be tested with
Hanbury-Brown and Twiss type interference. The second-order visibility of such
interference can provide an experimental test of entanglement. It is shown that
time-resolved interference leads to the Hong, Ou and Mandel deep, that provides
a signature of quantum non-separability for pure and mixed EPR states. A
Hanbury-Brown and Twiss type witness operator can be constructed to test the
quantum nature of the EPR entanglement.Comment: 9 pages, 5 figure
Interference fringes with maximal contrast at finite coherence time
Interference fringes can result from the measurement of four-time fourth-order correlation functions of a wave field. These fringes have a statistical origin and, as a consequence, they show the greatest contrast when the coherence time of the field is finite. A simple acoustic experiment is presented in which these fringes are observed, and it is demonstrated that the contrast is maximal for partial coherence. Random telegraph phase noise is used to vary the field coherence in order to highlight the problem of interpreting this interference; for this noise, the Gaussian moment theorem may not be invoked to reduce the description of the interference to one in terms of first-order interference.M.W. Hamilto
The Bose-Einstein distribution functions and the multiparticle production at high energies
The evolution properties of propagating particles produced at high energies
in a randomly distributed environment are studied. The finite size of the phase
space of the multiparticle production region as well as the chaoticity can be
derived.Comment: 18 pages, LaTeX, no figures, no table
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