Photonic quantum transport in a nonlinear optical fiber

We theoretically study the transmission of few-photon quantum fields through a strongly nonlinear optical medium. We develop a general approach to investigate nonequilibrium quantum transport of bosonic fields through a finite-size nonlinear medium and apply it to a recently demonstrated experimental system where cold atoms are loaded in a hollow-core optical fiber. We show that when the interaction between photons is effectively repulsive, the system acts as a single-photon switch. In the case of attractive interaction, the system can exhibit either antibunching or bunching, associated with the resonant excitation of bound states of photons by the input field. These effects can be observed by probing statistics of photons transmitted through the nonlinear fiber

Fitting Precision Electroweak Data with Exotic Heavy Quarks

The 1999 precision electroweak data from LEP and SLC persist in showing some slight discrepancies from the assumed standard model, mostly regarding $b$ and $c$ quarks. We show how their mixing with exotic heavy quarks could result in a more consistent fit of all the data, including two unconventional interpretations of the top quark.Comment: 7 pages, no figure, 2 typos corrected, 1 reference update

Intensity dependences of the nonlinear optical excitation of plasmons in graphene

Recently, we demonstrated an all-optical coupling scheme for plasmons, which takes advantage of the intrinsic nonlinear optical response of graphene. Frequency mixing using free-space, visible light pulses generates surface plasmons in a planar graphene sample, where the phase matching condition can define both the wavevector and energy of surface waves and intraband transitions. Here, we also show that the plasmon generation process is strongly intensity-dependent, with resonance features washed out for absorbed pulse fluences greater than 0.1 J m−2. This implies a subtle interplay between the nonlinear generation process and sample heating. We discuss these effects in terms of a non-equilibrium charge distribution using a two-temperature model.Peer ReviewedPostprint (author's final draft

Effects of viscosity and external constraints on wave transmission in blood vessels

Viscosity and external constraints studied for effects on wave transmission in blood vessel

Decay of Z into Three Pseudoscalar Bosons

We consider the decay of the $Z$ boson into three pseudoscalar bosons in a general two-Higgs-doublet model. Assuming $m_A$ to be very small, and that of the two physical neutral scalar bosons $h_1$ and $h_2$, $A$ only couples to $Z$ through $h_1$, we find the $Z \to A A A$ branching fraction to be negligible for moderate values of $\tan \beta \equiv v_2/v_1$, if there is no $\lambda_5 (\Phi_1^\dagger \Phi_2)^2 + h.c.$ term in the Higgs potential; otherwise there is no absolute bound but very large quartic couplings (beyond the validity of perturbation theory) are needed for it to be observable.Comment: 8 pages including 1 fi

Trapping atoms using nanoscale quantum vacuum forces

Quantum vacuum forces dictate the interaction between individual atoms and dielectric surfaces at nanoscale distances. For example, their large strengths typically overwhelm externally applied forces, which makes it challenging to controllably interface cold atoms with nearby nanophotonic systems. Here, we show that it is possible to tailor the vacuum forces themselves to provide strong trapping potentials. The trapping scheme takes advantage of the attractive ground state potential and adiabatic dressing with an excited state whose potential is engineered to be resonantly enhanced and repulsive. This procedure yields a strong metastable trap, with the fraction of excited state population scaling inversely with the quality factor of the resonance of the dielectric structure. We analyze realistic limitations to the trap lifetime and discuss possible applications that might emerge from the large trap depths and nanoscale confinement.Comment: 13 pages, 4 figure

Gestalt Theory in Visual Screen Design — A New Look at an old subject

Although often presented as a single basis for educational visual screen design, Gestalt theory is not a single small set of visual principles uniformly applied by all designers. In fact, it appears that instructional visual design literature often deals with only a small set of Gestalt laws. In this project Gestalt literature was consulted to distil the most relevant Gestalt laws for educational visual screen design. Eleven laws were identified. They deal with balance/symmetry, continuation, closure, figure-ground, focal point, isomorphic correspondence, prŠgnanz, proximity, similarity, simplicity, and unity/harmony. To test the usefulness of these laws in visual screen design they were applied to the redesign of an instructional multimedia application, 'WoundCare', designed to teach nursing students wound management. The basic text-based screens in the original WoundCare application were replaced with graphical user interface screens, that were designed according to these principles. The new screen designs were then evaluated by asking students and others to compare the designs. The viewers were also asked to rate directly the value of using the eleven Gestalt design principles in the redesign, both for improving the product's appearance and improving its value for learning. The evaluation results were overwhelmingly positive. Both the new design and the value of applying the eleven Gestalt laws to improve learning were strongly supported by the students' opinions. However, some differences in the value of applying particular Gestalt laws to the interface design were identified and this forms a useful direction for future research

Cavity QED with atomic mirrors

A promising approach to merge atomic systems with scalable photonics has emerged recently, which consists of trapping cold atoms near tapered nanofibers. Here, we describe a novel technique to achieve strong, coherent coupling between a single atom and photon in such a system. Our approach makes use of collective enhancement effects, which allow a lattice of atoms to form a high-finesse cavity within the fiber. We show that a specially designated "impurity" atom within the cavity can experience strongly enhanced interactions with single photons in the fiber. Under realistic conditions, a "strong coupling" regime can be reached, wherein it becomes feasible to observe vacuum Rabi oscillations between the excited impurity atom and a single cavity quantum. This technique can form the basis for a scalable quantum information network using atom-nanofiber systems.Comment: 20 pages, 4 figure

Arthropod diversity in peas with normal or reduced waxy bloom

Crop traits can alter economically important interactions between plants, pests, and biological control agents. For example, a reduced waxy bloom on the surface of pea plants alters interactions between pea aphids and their natural enemies. In this study, we assess whether the effect of wax reduction extends beyond the 2 or 3 arthropod species closely associated with the plants and into the structure of the broader arthropod community of over 200 taxa at our site. We sampled arthropods on lines of peas with normal and reduced wax in Latah Co., Idaho using pitfall traps within randomly assigned pairs of 5 × 5 meter plots. During the 1998 and 1999 growing seasons, we collected 12,113 individual arthropods from 221 unambiguously identified morphospecies. The number of individuals collected from each morphospecies responded idiosyncratically to the reduced wax peas. To test whether arthropod community structure differed between the collections from plots having peas with normal or reduced wax, we performed a randomization test. The collection from peas with reduced wax had higher species evenness and thus higher community diversity despite having lower species richness. Our results demonstrate the potential of a single plant trait, epicuticular wax, to affect a community of arthropods. Two pests of peas had opposite responses to peas with reduced wax. The number of pea aphids collected was greater from peas with normal wax peas than those with reduced wax. In contrast, the number of pea leaf weevils collected was greater from peas with reduced wax