4,463 research outputs found
Finite time St\"uckelberg interferometry with nanomechanical modes
St\"uckelberg interferometry describes the interference of two strongly
coupled modes during a double passage through an avoided energy level crossing.
In this work, we experimentally investigate finite time effects in
St\"uckelberg interference and provide an exact analytical solution of the
St\"uckelberg problem. Approximating this solution in distinct limits reveals
uncharted parameter regimes of St\"uckelberg interferometry. Experimentally, we
study these regimes using a purely classical, strongly coupled nanomechanical
two-mode system of high quality factor. The classical two-mode system consists
of the in-plane and out-of-plane fundamental flexural mode of a high stress
silicon nitride string resonator, coupled via electric gradient fields. The
dielectric control and microwave cavity enhanced universal transduction of the
nanoelectromechanical system allows for the experimental access to all
theoretically predicted St\"uckelberg parameter regimes. We exploit our
experimental and theoretical findings by studying the onset of St\"uckelberg
interference in dependence of the characteristic system control parameters and
obtain characteristic excitation oscillations between the two modes even
without the explicit need of traversing the avoided crossing. The presented
theory is not limited to classical mechanical two-mode systems but can be
applied to every strongly coupled (quantum) two-level system, for example a
spin-1/2 system or superconducting qubit
Coherent control of a nanomechanical two-level system
The Bloch sphere is a generic picture describing a coupled two-level system
and the coherent dynamics of its superposition states under control of
electromagnetic fields. It is commonly employed to visualise a broad variety of
phenomena ranging from spin ensembles and atoms to quantum dots and
superconducting circuits. The underlying Bloch equations describe the state
evolution of the two-level system and allow characterising both energy and
phase relaxation processes in a simple yet powerful manner.
Here we demonstrate the realisation of a nanomechanical two-level system
which is driven by radio frequency signals. It allows to extend the above Bloch
sphere formalism to nanoelectromechanical systems. Our realisation is based on
the two orthogonal fundamental flexural modes of a high quality factor
nanostring resonator which are strongly coupled by a dielectric gradient field.
Full Bloch sphere control is demonstrated via Rabi, Ramsey and Hahn echo
experiments. This allows manipulating the classical superposition state of the
coupled modes in amplitude and phase and enables deep insight into the
decoherence mechanisms of nanomechanical systems. We have determined the energy
relaxation time T1 and phase relaxation times T2 and T2*, and find them all to
be equal. This not only indicates that energy relaxation is the dominating
source of decoherence, but also demonstrates that reversible dephasing
processes are negligible in such collective mechanical modes. We thus conclude
that not only T1 but also T2 can be increased by engineering larger mechanical
quality factors. After a series of ground-breaking experiments on ground state
cooling and non-classical signatures of nanomechanical resonators in recent
years, this is of particular interest in the context of quantum information
processing
Signatures of two-level defects in the temperature-dependent damping of nanomechanical silicon nitride resonators
The damping rates of high quality factor nanomechanical resonators are well
beyond intrinsic limits. Here, we explore the underlying microscopic loss
mechanisms by investigating the temperature-dependent damping of the
fundamental and third harmonic transverse flexural mode of a doubly clamped
silicon nitride string. It exhibits characteristic maxima reminiscent of
two-level defects typical for amorphous materials. Coupling to those defects
relaxes the momentum selection rules, allowing energy transfer from discrete
long wavelength resonator modes to the high frequency phonon environment
Influence of Dietary Incorporation of Bloodmeal on Nursery Pig Manure Composition and Odor
Specific dietary ingredients may have the potential to alter manure odor by altering digestive patterns or fermentation or by masking manure odorants. Inclusion of dietary bloodmeal (BM) into nursery pig diets resulted in a slight, but insignificant, increase in manure odor intensity. Electronic nose response to manure odor moderately mimicked human response
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Evaluating LAB@FUTURE, a collaborative e-learning Laboratory experiments platform
This paper presents Lab@Future, an advanced e-learning platform that uses novel Information and Communication Technologies to support and expand laboratory teaching practices. For this purpose, Lab@Future uses real and computer generated objects that are interfaced using mechatronic systems, augmented reality, mobile technologies and 3D multi user environments. The main aim is to develop and demonstrate technological support for practical experiments in the following focused disciplines namely: Fluid Dynamics - Science subject in Germany, Geometry - Mathematics subject in Austria, History and Environmental Awareness – Arts and Humanities subjects in Greece and Slovenia. In order to pedagogically enhance the design and functional aspects of this e-learning technology, we are investigating the dialogical operationalisation of learning theories so as to leverage our understanding of teaching and learning practices in the targeted context of deployment. To be able to evaluate the lab@future system in its entire complexity an evaluation methodology including several phases has been developed, performing formative as well as summative evaluations
Non-malleable codes for space-bounded tampering
Non-malleable codes—introduced by Dziembowski, Pietrzak and Wichs at ICS 2010—are key-less coding schemes in which mauling attempts to an encoding of a given message, w.r.t. some class of tampering adversaries, result in a decoded value that is either identical or unrelated to the original message. Such codes are very useful for protecting arbitrary cryptographic primitives against tampering attacks against the memory. Clearly, non-malleability is hopeless if the class of tampering adversaries includes the decoding and encoding algorithm. To circumvent this obstacle, the majority of past research focused on designing non-malleable codes for various tampering classes, albeit assuming that the adversary is unable to decode. Nonetheless, in many concrete settings, this assumption is not realistic
Pneumococcal Serotype-Specific Antibodies Persist through Early Childhood after Infant Immunization: Follow-Up from a Randomized Controlled Trial
Background: In a previous UK multi-center randomized study 278 children received three doses of 7-valent (PCV-7) or 13-
valent (PCV-13) pneumococcal conjugate vaccine at 2, 4 and 12 months of age. At 13 months of age, most of these children had pneumococcal serotype-specific IgG concentrations 8.
Methods: Children who had participated in the original study were enrolled again at 3.5 years of age. Persistence of immunity following infant immunization with either PCV-7 or PCV-13 and the immune response to a PCV-13 booster at preschool age were investigated.
Results: In total, 108 children were followed-up to the age of 3.5 years and received a PCV-13 booster at this age. At least 76% of children who received PCV-7 or PCV-13 in infancy retained serotype-specific IgG concentrations 0.35 mg/ml against each of 4/6 of the additional PCV-13 serotypes; for serotypes 1 and 3 this proportion was 45% and 52%. In the PCV-7 group these percentages were significantly lower for serotypes 1, 5 and 7F. A pre-school PCV-13 booster was highly immunogenic and resulted in low rates of local and systemic adverse effects.
Conclusion: Despite some decline in antibody from 13 months of age, these data suggest that a majority of pre-school
children maintain protective serotype-specific antibody concentrations following conjugate vaccination at 2, 4 and 12 months of age.
Trial Registration: ClinicalTrials.gov NCT0109547
Efficient public-key cryptography with bounded leakage and tamper resilience
We revisit the question of constructing public-key encryption and signature schemes with security in the presence of bounded leakage and tampering memory attacks. For signatures we obtain the first construction in the standard model; for public-key encryption we obtain the first construction free of pairing (avoiding non-interactive zero-knowledge proofs). Our constructions are based on generic building blocks, and, as we show, also admit efficient instantiations under fairly standard number-theoretic assumptions.
The model of bounded tamper resistance was recently put forward by DamgĂĄrd et al. (Asiacrypt 2013) as an attractive path to achieve security against arbitrary memory tampering attacks without making hardware assumptions (such as the existence of a protected self-destruct or key-update mechanism), the only restriction being on the number of allowed tampering attempts (which is a parameter of the scheme). This allows to circumvent known impossibility results for unrestricted tampering (Gennaro et al., TCC 2010), while still being able to capture realistic tampering attack
Non-adiabatic dynamics of two strongly coupled nanomechanical resonator modes
The Landau-Zener transition is a fundamental concept for dynamical quantum
systems and has been studied in numerous fields of physics. Here we present a
classical mechanical model system exhibiting analogous behaviour using two
inversely tuneable, strongly coupled modes of the same nanomechanical beam
resonator. In the adiabatic limit, the anticrossing between the two modes is
observed and the coupling strength extracted. Sweeping an initialized mode
across the coupling region allows mapping of the progression from diabatic to
adiabatic transitions as a function of the sweep rate
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