926 research outputs found
Polarization entangled state measurement on a chip
The emerging strategy to overcome the limitations of bulk quantum optics
consists of taking advantage of the robustness and compactness achievable by
the integrated waveguide technology. Here we report the realization of a
directional coupler, fabricated by femtosecond laser waveguide writing, acting
as an integrated beam splitter able to support polarization encoded qubits.
This maskless and single step technique allows to realize circular transverse
waveguide profiles able to support the propagation of Gaussian modes with any
polarization state. Using this device, we demonstrate the quantum interference
with polarization entangled states and singlet state projection.Comment: Revtex, 5+2 pages (with supplementary information), 4+1 figure
Multi-path entanglement of two photons
We present a novel optical device based on an integrated system of
micro-lenses and single mode optical fibers. It allows to collect and direct
into many modes two photons generated by spontaneous parametric down
conversion. By this device multiqubit entangled states and/or multilevel
qu-it states of two photons, encoded in the longitudinal momentum degree of
freedom, are created. The multi-path photon entanglement realized by this
device is expected to find important applications in modern quantum information
technology.Comment: 4 pages, 3 figures, revtex, revised versio
Functional characterization and structure-guided mutational analysis of the transsulfuration enzyme cystathionine Îł-lyase from toxoplasma gondii
Sulfur-containing amino acids play essential roles in many organisms. The protozoan parasite Toxoplasma gondii includes the genes for cystathionine β-synthase and cystathionine γ-lyase (TgCGL), as well as for cysteine synthase, which are crucial enzymes of the transsulfuration and de novo pathways for cysteine biosynthesis, respectively. These enzymes are specifically expressed in the oocyst stage of T. gondii. However, their functionality has not been investigated. Herein, we expressed and characterized the putative CGL from T. gondii. Recombinant TgCGL almost exclusively catalyses the α,γ-hydrolysis of L-cystathionine to form L-cysteine and displays marginal reactivity toward L-cysteine. Structure-guided homology modelling revealed two striking amino acid differences between the human and parasite CGL active-sites (Glu59 and Ser340 in human to Ser77 and Asn360 in toxoplasma). Mutation of Asn360 to Ser demonstrated the importance of this residue in modulating the specificity for the catalysis of α,β-versus α,γ-elimination of L-cystathionine. Replacement of Ser77 by Glu completely abolished activity towards L-cystathionine. Our results suggest that CGL is an important functional enzyme in T. gondii, likely implying that the reverse transsulfuration pathway is operative in the parasite; we also probed the roles of active-site architecture and substrate binding conformations as determinants of reaction specificity in transsulfuration enzymes
Proposal for an Optical Test of the Einstein Equivalence Principle
The Einstein Equivalence Principle (EEP) underpins all metric theories of
gravity. Its key element is the local position invariance of non-gravitational
experiments, which entails the gravitational red-shift. Precision measurements
of the gravitational red-shift tightly bound violations of the EEP only in the
fermionic sector of the Standard Model, however recent developments of
satellite optical technologies allow for its investigation in the
electromagnetic sector. Proposals exploiting light interferometry traditionally
suffer from the first-order Doppler effect, which dominates the weak
gravitational signal necessary to test the EEP, making them unfeasible. Here,
we propose a novel scheme to test the EEP, which is based on a double
large-distance optical interferometric measurement. By manipulating the
phase-shifts detected at two locations at different gravitational potentials it
is possible to cancel-out the first-order Doppler effect and observe the
gravitational red-shift implied by the EEP. We present the detailed analysis of
the proposal within the post-Newtonian framework and the simulations of the
expected signals obtained by using two realistic satellite orbits. Our proposal
to overcome the first-order Doppler effect in optical EEP tests is feasible
with current technology.Comment: manuscript improve
Engineering a C-Phase quantum gate: optical design and experimental realization
A two qubit quantum gate, namely the C-Phase, has been realized by exploiting
the longitudinal momentum (i.e. the optical path) degree of freedom of a single
photon. The experimental setup used to engineer this quantum gate represents an
advanced version of the high stability closed-loop interferometric setup
adopted to generate and characterize 2-photon 4-qubit Phased Dicke states. Some
experimental results, dealing with the characterization of multipartite
entanglement of the Phased Dicke states are also discussed in detail.Comment: accepted for publication on EPJ
Large-scale optical interferometry in general spacetimes
We introduce a convenient formalism to evaluate the frequency-shift affecting
a light signal propagating on a general curved background. Our formulation,
which is based on the laws of geometric optics in a general relativistic
setting, allows to obtain a transparent generalization of the Doppler
frequency-shift without requiring to perform Local Lorentz transformations. It
is easily applicable to stationary spacetimes, and in particular to the
near-Earth experiments where geometry is described in the parametrized
post-Newtonian approximation. We apply our recipe to evaluate the phase-shift
arising in large-scale optical interferometric experiments, as the optical
version of the Colella-Overhauser-Werner experiment.Comment: 8 pages, 3 figure
Thyroid ultrasonography reporting: consensus of Italian Thyroid Association (AIT), Italian Society of Endocrinology (SIE), Italian Society of Ultrasonography in Medicine and Biology (SIUMB) and Ultrasound Chapter of Italian Society of Medical Radiology (SIRM)
Thyroid ultrasonography (US) is the gold standard for thyroid imaging and its widespread use is due to an optimal spatial resolution for superficial anatomic structures, a low cost and the lack of health risks. Thyroid US is a pivotal tool for the diagnosis and follow-up of autoimmune thyroid diseases, for assessing nodule size and echostructure and defining the risk of malignancy in thyroid nodules. The main limitation of US is the poor reproducibility, due to the variable experience of the operators and the different performance and settings of the equipments. Aim of this consensus statement is to standardize the report of thyroid US through the definition of common minimum requirements and a correct terminology. US patterns of autoimmune thyroid diseases are defined. US signs of malignancy in thyroid nodules are classified and scored in each nodule. We also propose a simplified nodule risk stratification, based on the predictive value of each US sign, classified and scored according to the strength of association with malignancy, but also to the estimated reproducibility among different operators
Underpowered Aircraft - Performance and Operational Possibilities
A unique configuration, known as an Underpowered Aircraft, allows for the modification of gliding flight vehicles for increased range and lower cost when compared with fully powered flight vehicles. Intentionally under-sizing the powerplant for a flight vehicle allows the designer to choose a powerplant that will not only perform the mission requirements, but will also provide the customer with the most cost effective solution, as some missions may not require fully powered flight. Specifically, the underpowered aircraft concept studied in this paper is a gliding flight aircraft that does not have enough power for climbing or level flight, but does have enough power to overcome some of the drag forces associated with flight, in turn increasing the effective range of the vehicle. In this paper, the underpowered aircraft concept was analyzed and its feasibility was determined. Analysis done using equations of motion, followed by a more accurate numerical integration including a thrust lapse, determined that the underpowered aircraft concept provides a unique method for a cost effective range extension technology for gliding flight vehicles. Finally, the technology and methods of this paper were applied to the AGM-154 JSOW and JSOW-ER glide munitions and it was determined that JSOW-ER is representative of an underpowered aircraft with our analysis. This paper represents a back-of-the-envelope investigation into the underpowered aircraft concept
On the numerical assessment of the thermal-hydraulic operating map of the DEMO Divertor Plasma Facing Components cooling circuit
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