Thermoplasmonics: Quantifying plasmonic heating in single nanowires

Plasmonic absorption of light can lead to significant local heating in metallic nanostructures, an effect that defines the sub-field of thermoplasmonics and has been leveraged in diverse applications from biomedical technology to optoelectronics. Quantitatively characterizing the resulting local temperature increase can be very challenging in isolated nanostructures. By measuring the optically-induced change in resistance of metal nanowires with a transverse plasmon mode, we quantitatively determine the temperature increase in single nanostructures, with the dependence on incident polarization clearly revealing the plasmonic heating mechanism. Computational modeling explains the resonant and nonresonant contributions to the optical heating and the dominant pathways for thermal transport. These results, obtained by combining electronic and optical measurements, place a bound on the role of optical heating in prior experiments, and suggest design guidelines for engineered structures meant to leverage such effects.Comment: 17 pages, 4 figures + 3 pages supporting materia

Realistic lower bounds for the factorization time of large numbers on a quantum computer.

Published versio

Hot entanglement in a simple dynamical model

How mixed can one component of a bi-partite system be initially and still become entangled through interaction with a thermalized partner? We address this question here. In particular, we consider the question of how mixed a two-level system and a field mode may be such that free entanglement arises in the course of the time evolution according to a Jaynes-Cummings type interaction. We investigate the situation for which the two-level system is initially in mixed state taken from a one-parameter set, whereas the field has been prepared in an arbitrary thermal state. Depending on the particular choice for the initial state and the initial temperature of the quantised field mode, three cases can be distinguished: (i) free entanglement will be created immediately, (ii) free entanglement will be generated, but only at a later time different from zero, (iii) the partial transpose of the joint state remains positive at all times. It will be demonstrated that increasing the initial temperature of the field mode may cause the joint state to become distillable during the time evolution, in contrast to a non-distillable state at lower initial temperatures. We further assess the generated entanglement quantitatively, by evaluating the logarithmic negativity numerically, and by providing an analytical upper bound.Comment: 5 pages, 2 figures. Contribution to the proceedings of the 'International Conference on Quantum Information', Oviedo, July 13-18, 2002. Discusses sudden changes of entanglement properties in a dynamical quantum mode

On the Preparation of Pure States in Resonant Microcavities

We consider the time evolution of the radiation field (R) and a two-level atom (A) in a resonant microcavity in terms of the Jaynes-Cummings model with an initial general pure quantum state for the radiation field. It is then shown, using the Cauchy-Schwarz inequality and also a Poisson resummation technique, that {\it perfect} coherence of the atom can in general never be achieved. The atom and the radiation field are, however, to a good approximation in a pure state $|\psi >_A\otimes|\psi >_R$ in the middle of what has been traditionally called the ``collapse region'', independent of the initial state of the atoms, provided that the initial pure state of the radiation field has a photon number probability distribution which is sufficiently peaked and phase differences that do not vary significantly around this peak. An approximative analytic expression for the quantity \Tr[\rho^2_{A}(t)], where $\rho_{A}(t)$ is the reduced density matrix for the atom, is derived. We also show that under quite general circumstances an initial entangled pure state will be disentangled to the pure state $|\psi >_{A\otimes R}$.Comment: 14 pages and 3 figure

Depth-averaged simulation of flows in asymmetric compound channels with smooth and rough narrow floodplains

Depth-averaged hydrodynamic models are predominantly used in numerical simulations of compound channel flows. One of the most popular methods for the depth-averaged simulation is Shiono and Knight method (SKM). This method accounts for the effects of bed friction, lateral turbulence and secondary flows, via three key parameters f, λ and Γ, respectively. The conventional expressions that are developed to calibrate these parameters are generally based on experiments in compound channels with wide floodplains. In this study, the application of SKM to an asymmetric compound channel with a narrow floodplain is examined in terms of the calibration requirements. Two sets of experiments that have smooth and rough floodplains are conducted and then simulated by SKM. In smooth floodplain cases, the results reveal that SKM model with the conventional calibration expressions of f, λ and Г is reasonably capable of predicting the distributions of depth-averaged velocity and boundary shear stress in the main channel. However, in the floodplain region, the expressions recommended for calibrating Г need to be modified to improve the predicted results in that region. In cases of the rough floodplain, the results indicate that only the values of λ in the main channel need to be changed from its conventional values to improve the predictions

A Research-Based Curriculum for Teaching the Photoelectric Effect

Physics faculty consider the photoelectric effect important, but many erroneously believe it is easy for students to understand. We have developed curriculum on this topic including an interactive computer simulation, interactive lectures with peer instruction, and conceptual and mathematical homework problems. Our curriculum addresses established student difficulties and is designed to achieve two learning goals, for students to be able to (1) correctly predict the results of photoelectric effect experiments, and (2) describe how these results lead to the photon model of light. We designed two exam questions to test these learning goals. Our instruction leads to better student mastery of the first goal than either traditional instruction or previous reformed instruction, with approximately 85% of students correctly predicting the results of changes to the experimental conditions. On the question designed to test the second goal, most students are able to correctly state both the observations made in the photoelectric effect experiment and the inferences that can be made from these observations, but are less successful in drawing a clear logical connection between the observations and inferences. This is likely a symptom of a more general lack of the reasoning skills to logically draw inferences from observations.Comment: submitted to American Journal of Physic

Mountain Pine Beetle Outbreaks in the Rocky Mountains: Regulators of Primary Productivity?

We consider the hypothesis that mountain pine beetles function as cybernetic regulators of primary productivity in ecosystems of lodgepole pine forest through their selective killing of dominant trees and the subsequent redistribution of resources. Following a recent major beetle outbreak in Yellowstone and Grand Teton national parks, surviving trees did grow significantly faster (P \u3c .1); wood production was redistributed among canopy, subcanopy, and understory trees; and annual wood production per hectare usually returned to pre-attack levels or exceeded them within 10-15 yr. However, reconstructions of annual wood production over the last 70-80 yr indicate that the beetle outbreak did not reduce the variation in productivity; rather, the beetles introduced more variation than would have existed in their absence. Hence, our results do not support the hypothesis that the beetles function as cybernetic regulators (in the strict sense). Nevertheless, the beetle-pine system that we studied shows great resilience, and the effects of beetles on primary productivity do not appear to be as severe as conventional wisdom maintains. Annual wood production per hectare returned quickly to previous levels in the stands we studied, and associated ecological changes can be considered generally benign or even beneficial

The Effects of Thawing Procedure and Supplementation on the Motility and Viability of Frozen-thawed Boar Semen

The effect of two thawing procedures on frozen boar semen and supplementations to the fertilization media were studied. Frozen boar semen was thawed using either Percoll gradient or phosphate buffered saline (PBS)procedure. Supplementations were 1.0 mM L-glutamate, 1.0 mM N-acetylcysteine (NAC) , and 1.0 mM NAC-amide (NACA). Spermatozoa were analyzed for forward progressive motility (FPM) and viability every 0.5 h for 3 .0 h post-thawing. There were significantly (P \u3c 0.05) higher numbers of viable (76.0 ± 5.1 %) and FPM (30 .0 ± 2.4%) spermatozoa at 3.0 h post thawing using the PBS procedure compared to the Percoll gradient thawed spermatozoa (65.0 ± 3.9%; 10.0 ± 4.5 %, respectively). Supplementation of 1.0 mM L-glutamate, 1.0 mM NAC, or 1.0 mM NACA had no significant effect on spermatozoa viability regardless of the time post-thaw.Supplementation of 1.0 mM L-glutamate, 1.0 mM NAC , or 1.0 mM NACA had no significant effect on FPM up to 1.0 h post-thaw. Spermatozoa with no supplementation or 1.0 mM L-glutamate had significantly higher (P \u3c 0.05) FPM compared to the 1.0 mM NAC and 1.0 mM NACA supplemented groups at 1.5, 2.0, 2 .5, and 3.0 h post-thaw. There was no significant difference between no supplementation or 1.0 mM L-glutamate on FPM regardless of the time post-thaw. There was no significant difference between 1.0 mM NAC or 1.0 mM NACA on FPM regardless of the time post-thaw. These results indicate that thawing procedure has an effect on spermatozoa viability and FPM but supplementation does not have an effect on the overall viability of spermatozoa during thawing, but may reduce FPM