575 research outputs found
Continuous variable remote state preparation
We extend exact deterministic remote state preparation (RSP) with minimal
classical communication to quantum systems of continuous variables. We show
that, in principle, it is possible to remotely prepare states of an ensemble
that is parameterized by infinitely many real numbers, i.e., by a real
function, while the classical communication cost is one real number only. We
demonstrate continuous variable RSP in three examples using (i) quadrature
measurement and phase space displacement operations, (ii) measurement of the
optical phase and unitaries shifting the same, and (iii) photon counting and
photon number shift.Comment: 7 pages, RevTeX
Production of photon states from Λ-atoms in a cavity
We analyse the system of Λ-atoms in a cavity QED of semi-transparent mirror and driven by laser fields. We derive effective models and connect concepts (photonic flux, input-output operators, photonic state) characterizing the propagation of the resulting leaking photons. We propose an atom-cavity non-resonant scheme for single-and 2-photons generation. The pulse shapes of outgoing single photons are tailored using a specifically designed driving field envelope. For the production of 2-photon states, two trapped atoms are used with two driving pulses. Their pulse shapes are characterized and it is shown that the multiphoton outgoing photonic states cannot be Fock states, since the photons are not generated strictly simultaneously
Stimulated Raman Adiabatic Passage (STIRAP) Among Degenerate-Level Manifolds
We examine the conditions needed to accomplish stimulated Raman adiabatic
passage (STIRAP) when the three levels (g, e and f) are degenerate, with
arbitrary couplings contributing to the pump-pulse interaction (g - e) and to
the Stokes-pulse interaction (e-f). We show that in general a sufficient
condition for complete population removal from the g set of degenerate states
for arbitrary, pure or mixed, initial state is that the degeneracies should not
decrease along the sequence g, e and f. We show that when this condition holds
it is possible to achieve the degenerate counterpart of conventional STIRAP,
whereby adiabatic passage produces complete population transfer. Indeed, the
system is equivalent to a set of independent three-state systems, in each of
which a STIRAP procedure can be implemented. We describe a scheme of unitary
transformations that produces this result. We also examine the cases when this
degeneracy constraint does not hold, and show what can be accomplished in those
cases. For example, for angular momentum states when the degeneracy of the g
and f levels is less than that of the e level we show how a special choice for
the pulse polarizations and phases can produce complete removal of population
from the g set. Our scheme can be a powerful tool for coherent control in
degenerate systems, because of its robustness when selective addressing of the
states is not required or impossible. We illustrate the analysis with several
analytically solvable examples, in which the degeneracies originate from
angular momentum orientation, as expressed by magnetic sublevels.Comment: 21 pages, 17 figure
Could vectors’ fear of predators reduce the spread of plant diseases?
AbstractPredators influence the behaviour of prey and by doing so they potentially reduce pathogen transmission by a vector. Arthropod predators have been shown to reduce the consumption of plant biomass by pest herbivores, but their cascading non-consumptive effect on vector insects’ feeding behaviour and subsequent pathogen transmission has not been investigated experimentally before. Here we experimentally examined predator-mediated pathogen transmission mechanisms using the plant pathogen Wheat Dwarf Virus that is transmitted by the leafhopper, Psammotettix alienus. We applied in situ hybridization to localize which leaf tissues were infected with transmitted virus DNA in barley host plants, proving that virus occurrence is restricted to phloem tissues. In the presence of the spider predator, Tibellus oblongus, we recorded the within leaf feeding behaviour of the herbivore using electrical penetration graph. The leafhopper altered its feeding behaviour in response to predation risk. Phloem ingestion, the feeding phase when virus acquisition occurs, was delayed and was less frequent. The phase when pathogen inoculation takes place, via the secretion of virus infected vector saliva, was shorter when predator was present. Our study thus provides experimental evidence that predators can potentially limit the spread of plant pathogens solely through influencing the feeding behaviour of vector organisms.</jats:p
Response to comments on "Differential Sensitivity to Human Communication in Dogs, Wolves, and Human Infants."
The comments by Fiset and Marshall-Pescini et al. raise important methodological issues and propose alternative accounts for our finding of perseverative search errors in dogs. Not denying that attentional processes and local enhancement are involved in such object search tasks, we provide here new evidence and argue that dogs’ behavior is affected by a combination of factors, including specific susceptibility to human communicative signals
Vibrational Schroedinger Cats
The optical Schroedinger cat states are simple realizations of quantum states having nonclassical features. It is shown that vibrational analogues of such states can be realized in an experiment of double pulse excitation of vibrionic transitions. To track the evolution of the vibrational wave packet we derive a non-unitary time evolution operator so that calculations are made in a quasi Heisenberg picture
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