423 research outputs found
Quantum theory of electron tunneling into intersubband cavity polariton states
Through a non-perturbative quantum theory, we investigate how the
quasi-electron excitations of a two-dimensional electron gas are modified by
strong coupling to the vacuum field of a microcavity. We show that the
electronic dressed states originate from a Fano-like coupling between the bare
electron states and the continuum of intersubband cavity polariton excitations.
In particular, we calculate the electron spectral function modified by
light-matter interactions and its impact on the electronic injection of
intersubband cavity polaritons. The domain of validity of the present
theoretical results is critically discussed. We show that resonant electron
tunneling from a narrow-band injector can selectively excite superradiant
states and produce efficient intersubband polariton electroluminescence
Positronium density measurements using polaritonic effects
Recent experimental advances in positronium (Ps) physics have made it possible to produce dense Ps ensembles in which Ps-Ps interactions may occur, leading to the production of Ps2 molecules and paving the way to the realization of a Ps Bose-Einstein condensate (BEC). In order to achieve this latter goal it would be advantageous to develop new methods to measure Ps densities in real time. Here we describe a possible approach to do this using polaritonic methods: Using realistic experimental parameters, we demonstrate that a dense Ps gas can be strongly coupled to the photonic field of a distributed Bragg reflector microcavity. In this strongly coupled regime, the optical spectrum of the system is composed of two hybrid positronium-polariton resonances separated by the vacuum Rabi splitting, which is proportional to the square root of the Ps density. Given that polaritons can be created on a subcycle timescale, a spectroscopic measurement of the vacuum Rabi splitting could be used as an ultrafast Ps density measurement in regimes relevant to Ps BEC formation. Moreover, we show how positronium polaritons could potentially enter the ultrastrong light-matter coupling regime, introducing a platform to explore its nonperturbative phenomenology
Light-matter decoupling and A2 term detection in superconducting circuits
APS March Meeting 2015, San Antonio, Texas, March 2–6, 2015We study the spontaneous emission of a qubit interacting with a one-dimensional waveguide through a realistic minimal-coupling interaction. We show that the diamagnetic term A2 leads to an effective decoupling of a single qubit from the electromagnetic field. This effect is observable at any range of qubit-photon couplings. For this we study a setup consisting of a transmon that is suspended over a transmission line. Assuming a standard model of qubit-line interaction, we prove that the relative strength of the A2 term is controlled with the qubit-line separation and show that, as a consequence, the spontaneous emission rate of the suspended transmon onto the line can increase with such separation, instead of decreasing.Peer Reviewe
Insights into the Structure of Dot@Rod and Dot@Octapod CdSe@CdS Heterostructures
CdSe@CdS dot@rods with diameter around 6 nm and length of either
20, 27, or 30 nm and dot@octapods with pod diameters of ?15 nm and lengths of ?50
nm were investigated by X-ray absorption spectroscopy. These heterostructures are
prepared by seed-mediated routes, where the structure, composition, and morphology of
the CdSe nanocrystals used as a seed play key roles in directing the growth of the second
semiconducting domain. The local structural environment of all the elements in the
CdSe@CdS heterostructures was investigated at the Cd, S, and Se K-edges by taking
advantage of the selectivity of X-ray absorption spectroscopy, and was compared to pure
reference compounds. We found that the structural features of dot@rods are
independent of the size of the rods. These structures can be described as made of a
CdSe dot and a CdS rod, both in the wurtzite phase with a high crystallinity of both the
core and the rod. This result supports the effectiveness of high temperature colloidal
synthesis in promoting the formation of core@shell nanocrystals with very low
defectivity. On the other hand, data on the CdSe@CdS with octapod morphology suggest the occurrence of a core composed of
a CdSe cubic sphalerite phase with eight pods made of CdS wurtzite phase. Our findings are compared to current models
proposed for the design of functional heterostructures with controlled nanoarchitecture
Dynamical Casimir effect in a Josephson metamaterial
Vacuum modes confined into an electromagnetic cavity give rise to an
attractive interaction between the opposite walls. When the distance between
the walls is changed non-adiabatically, virtual vacuum modes are turned into
real particles, i.e. photons are generated out of the vacuum. These effects are
known as the static and dynamical Casimir effect, respectively. Here we
demonstrate the dynamical Casimir effect using a Josephson metamaterial
embedded in a microwave cavity at 5.4 GHz. We achieve the non-adiabatic change
in the effective length of the cavity by flux-modulation of the SQUID-based
metamaterial, which results in a few percent variation in the velocity of
light. We show that energy-correlated photons are generated from the ground
state of the cavity and that their power spectra display a bimodal frequency
distribution. These results are in excellent agreement with theoretical
predictions, all the way to the regime where classical parametric effects
cannot be of consequence.Comment: 4 pages, 3 figures, supplement at http://ltl.tkk.fi/~pjh/DCE
Fermionized photons in an array of driven dissipative nonlinear cavities
We theoretically investigate the optical response of a one-dimensional array
of strongly nonlinear optical microcavities. When the optical nonlinearity is
much larger than both losses and inter-cavity tunnel coupling, the
non-equilibrium steady state of the system is reminiscent of a strongly
correlated Tonks-Girardeau gas of impenetrable bosons. Signatures of strong
correlations are identified in the absorption spectrum of the system, as well
as in the intensity correlations of the emitted light. Possible experimental
implementations in state-of-the-art solid-state devices are discussed
Morphological and molecular characterization of trichuris sp. (nematoda: Trichuridae) in crested porcupines (hystrix cristata; rodentia: Hystricidae) from Italy
Adult specimens of Trichuris sp. collected from crested porcupines (Hystrix cristata) from Italy were characterized using an integrative taxonomic approach involving morphological and molecular tools. The morphological features of this Trichuris sp. were compared to data already available for Trichuris spp. from Hystrix sp., revealing diagnostic traits, such as spicule length in males or vulva shape in females, which distinguish this Trichuris sp. from the other species. Evidence from sequences analysis of the partial mitochondrial COX1 region indicated that the taxon under study is a distinct lineage. Biometrical and genetic data suggested this Trichuris sp. to be a valid and separated taxon. However, since molecular data from other Trichuris spp. infecting Hystrix, such as T. infundibulus, T. hystricis, T. javanica, T. landak and T. lenkorani, are missing in public repositories, the number and identity of distinct lineages able to infect porcupines remain only partially defined
A study of the prevalence and genotypes of Giardia duodenalis infecting kennelled dogs
Giardia duodenalis is a protozoan parasite of animals that is zoonotic. Given the capacity of this organism to spread via the faecal–oral
route, animals held in overcrowded and unhygienic conditions are at high risk of infection. Faecal samples from dogs in three kennels in
Rome were examined by microscopy and PCR for G. duodenalis, and the prevalence data generated were correlated with variables such
as kennel identity, age of dog, length of time the dog had been kennelled and clinical signs.
The overall prevalence of the parasite in the faecal samples was 20.5% and was higher in samples from the largest kennel, which had
the greatest turnover of dogs, and in faecal samples from younger animals. Giardia cysts were found more frequently in diarrhoeic animals
but were also found in dogs with no clinical signs. Although the finding that the majority of isolates were dog-specific rather than
zoonotic genotypes suggests that the zoonotic risk from this pathogen is less than previously thought, the higher prevalence of infection
in younger dogs may pose a specific public health issue as such animals are more frequently re-homed with families.
2008 Elsevier Ltd. All rights reserved
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