5,217 research outputs found
A model of Poissonian interactions and detection of dependence
This paper proposes a model of interactions between two point processes,
ruled by a reproduction function h, which is considered as the intensity of a
Poisson process. In particular, we focus on the context of neurosciences to
detect possible interactions in the cerebral activity associated with two
neurons. To provide a mathematical answer to this specific problem of
neurobiologists, we address so the question of testing the nullity of the
intensity h. We construct a multiple testing procedure obtained by the
aggregation of single tests based on a wavelet thresholding method. This test
has good theoretical properties: it is possible to guarantee the level but also
the power under some assumptions and its uniform separation rate over weak
Besov bodies is adaptive minimax. Then, some simulations are provided, showing
the good practical behavior of our testing procedure.Comment: 27 page
Full counting statistics and phase diagram of a dissipative Rydberg gas
Ultra-cold gases excited to strongly interacting Rydberg states are a
promising system for quantum simulations of many-body systems. For off-resonant
excitation of such systems in the dissipative regime, highly correlated
many-body states exhibiting, among other characteristics, intermittency and
multi-modal counting distributions are expected to be created. So far,
experiments with Rydberg atoms have been carried out in the resonant,
non-dissipative regime. Here we realize a dissipative gas of rubidium Rydberg
atoms and measure its full counting statistics for both resonant and
off-resonant excitation. We find strongly bimodal counting distributions in the
off-resonant regime that are compatible with intermittency due to the
coexistence of dynamical phases. Moreover, we measure the phase diagram of the
system and find good agreement with recent theoretical predictions. Our results
pave the way towards detailed studies of many-body effects in Rydberg gases.Comment: 12 pages, 5 figure
Full photon statistics of a light beam transmitted through an optomechanical system
In this paper, we study the full statistics of photons transmitted through an
optical cavity coupled to nanomechanical motion. We analyze the entire temporal
evolution of the photon correlations, the Fano factor, and the effects of
strong laser driving, all of which show pronounced features connected to the
mechanical backaction. In the regime of single-photon strong coupling, this
allows us to predict a transition from sub-Poissonian to super-Poissonian
statistics for larger observation time intervals. Furthermore, we predict
cascades of transmitted photons triggered by multi-photon transitions. In this
regime, we observe Fano factors that are drastically enhanced due to the
mechanical motion.Comment: 8 pages, 7 figure
Strongly enhanced shot noise in chains of quantum dots
We study charge transport through a chain of quantum dots. The dots are fully
coherent among each other and weakly coupled to metallic electrodes via the
dots at the interface, thus modelling a molecular wire. If the non-local
Coulomb interactions dominate over the inter-dot hopping we find strongly
enhanced shot noise above the sequential tunneling threshold. The current is
not enhanced in the region of enhanced noise, thus rendering the noise
super-Poissonian. In contrast to earlier work this is achieved even in a fully
symmetric system. The origin of this novel behavior lies in a competition of
"slow" and "fast" transport channels that are formed due to the differing
non-local wave functions and total spin of the states participating in
transport. This strong enhancement may allow direct experimental detection of
shot noise in a chain of lateral quantum dots.Comment: 4 pages, 2 figures, submitted to PR
Direct Observation of Sub-Poissonian Number Statistics in a Degenerate Bose Gas
We report the direct observation of sub-Poissonian number fluctuation for a
degenerate Bose gas confined in an optical trap. Reduction of number
fluctuations below the Poissonian limit is observed for average numbers that
range from 300 to 60 atoms.Comment: 5 pages, 4 figure
An experimental approach for investigating many-body phenomena in Rydberg-interacting quantum systems
Recent developments in the study of ultracold Rydberg gases demand an
advanced level of experimental sophistication, in which high atomic and optical
densities must be combined with excellent control of external fields and
sensitive Rydberg atom detection. We describe a tailored experimental system
used to produce and study Rydberg-interacting atoms excited from dense
ultracold atomic gases. The experiment has been optimized for fast duty cycles
using a high flux cold atom source and a three beam optical dipole trap. The
latter enables tuning of the atomic density and temperature over several orders
of magnitude, all the way to the Bose-Einstein condensation transition. An
electrode structure surrounding the atoms allows for precise control over
electric fields and single-particle sensitive field ionization detection of
Rydberg atoms. We review two experiments which highlight the influence of
strong Rydberg--Rydberg interactions on different many-body systems. First, the
Rydberg blockade effect is used to pre-structure an atomic gas prior to its
spontaneous evolution into an ultracold plasma. Second, hybrid states of
photons and atoms called dark-state polaritons are studied. By looking at the
statistical distribution of Rydberg excited atoms we reveal correlations
between dark-state polaritons. These experiments will ultimately provide a
deeper understanding of many-body phenomena in strongly-interacting regimes,
including the study of strongly-coupled plasmas and interfaces between atoms
and light at the quantum level.Comment: 14 pages, 11 figures; submitted to a special issue of 'Frontiers of
Physics' dedicated to 'Quantum Foundation and Technology: Frontiers and
Future
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