Thermal limitation of far-field matter-wave interference

We assess the effect of the heat radiation emitted by mesoscopic particles on their ability to show interference in a double slit arrangement. The analysis is based on a stationary, phase-space based description of matter wave interference in the presence of momentum-exchange mediated decoherence.Comment: 8 pages, 2 figures; published versio

Decoherence suppression via environment preparation

To protect a quantum system from decoherence due to interaction with its environment, we investigate the existence of initial states of the environment allowing for decoherence-free evolution of the system. For models in which a two-state system interacts with a dynamical environment, we prove that such states exist if and only if the interaction and self-evolution Hamiltonians share an eigenstate. If decoherence by state preparation is not possible, we show that initial states minimizing decoherence result from a delicate compromise between the environment and interaction dynamics.Comment: 4 pages, 2 figure

A Monte Carlo Method for Modeling Thermal Damping: Beyond the Brownian-Motion Master Equation

The "standard" Brownian motion master equation, used to describe thermal damping, is not completely positive, and does not admit a Monte Carlo method, important in numerical simulations. To eliminate both these problems one must add a term that generates additional position diffusion. He we show that one can obtain a completely positive simple quantum Brownian motion, efficiently solvable, without any extra diffusion. This is achieved by using a stochastic Schroedinger equation (SSE), closely analogous to Langevin's equation, that has no equivalent Markovian master equation. Considering a specific example, we show that this SSE is sensitive to nonlinearities in situations in which the master equation is not, and may therefore be a better model of damping for nonlinear systems.Comment: 6 pages, revtex4. v2: numerical results for a nonlinear syste

Diffusive limit for a quantum linear Boltzmann dynamics

In this article, I study the diffusive behavior for a quantum test particle interacting with a dilute background gas. The model I begin with is a reduced picture for the test particle dynamics given by a quantum linear Boltzmann equation in which the gas particle scattering is assumed to occur through a hard-sphere interaction. The state of the particle is represented by a density matrix that evolves according to a translation-covariant Lindblad equation. The main result is a proof that the particle's position distribution converges to a Gaussian under diffusive rescaling.Comment: 51 pages. I have restructured Sections 2-4 from the previous version and corrected an error in the proof of Proposition 7.

Collisional decoherence observed in matter wave interferometry

We study the loss of spatial coherence in the extended wave function of fullerenes due to collisions with background gases. From the gradual suppression of quantum interference with increasing gas pressure we are able to support quantitatively both the predictions of decoherence theory and our picture of the interaction process. We thus explore the practical limits of matter wave interferometry at finite gas pressures and estimate the required experimental vacuum conditions for interferometry with even larger objects.Comment: 4 pages, 3 figure

Biomarkers of Heavy Metal Effects in Two Species of Caddisfly Larvae from Clark Fork River, Montana: Stress Proteins (HSP70) and Lysosomal Membrane Integrity

Potential sublethal effects of heavy metals in stream macroinvertebrates were examined with two cellular and biochemical biomarkers in larvae of two caddisflies indigenous to the Clark Fork River, Montana, - Hydropsyche spp. and Arctopsyche grandis. Stress proteins, in particular members of the HSP70 family, are involved in cellular protein homeostasis and repair, and are induced by a variety of stressors, which either damage cellular proteins directly or cause cells to synthesize aberrant proteins. Lysosomes are intracellular organelles that play key roles in the detoxification of both organic and inorganic xenobiotic compounds. Larvae of Hydropsyche spp. were collected from four sites on the Clark Fork (Galen Gage--4.7 km, Goldcreek--85.6 km, Turah--189.7 km, above Flathead--381 km) and a reference site (the Blackfoot River). Larvae of A. grandis were collected from the same sites minus the Galen site. Samples were immediately frozen in liquid nitrogen for HSP70 analysis, or preserved with Tissue Tek, then frozen in liquid nitrogen for the lysosomal stability assay. HSP70 was analyzed by western blotting using monoclonal antibodies. Lysosomal integrity was measured in cryosections by acid labilization with acid phosphatase as a marker enzyme. Results to date show elevated tissue concentrations of Cd, Cu, Pb and Zn and significantly increased levels of HSP70 in Arctopsyche from Goldcreek compared to reference samples. Lysosomal integrity also was compromised in samples from Goldcreek. In Hydropsyche, tissue concentrations of Cd, Cu and Pb from Galen Gage were elevated (4-7 times) relative to the Blackfoot River, but levels of HSP70 did not differ between the two sites. These preliminary results indicate that sublethal effects of metal exposure may differ between species

The wave nature of biomolecules and fluorofullerenes

We demonstrate quantum interference for tetraphenylporphyrin, the first biomolecule exhibiting wave nature, and for the fluorofullerene C60F48 using a near-field Talbot-Lau interferometer. For the porphyrins, which are distinguished by their low symmetry and their abundant occurence in organic systems, we find the theoretically expected maximal interference contrast and its expected dependence on the de Broglie wavelength. For C60F48 the observed fringe visibility is below the expected value, but the high contrast still provides good evidence for the quantum character of the observed fringe pattern. The fluorofullerenes therefore set the new mark in complexity and mass (1632 amu) for de Broglie wave experiments, exceeding the previous mass record by a factor of two.Comment: 5 pages, 4 figure

Colloquium: Quantum interference of clusters and molecules

We review recent progress and future prospects of matter wave interferometry with complex organic molecules and inorganic clusters. Three variants of a near-field interference effect, based on diffraction by material nanostructures, at optical phase gratings, and at ionizing laser fields are considered. We discuss the theoretical concepts underlying these experiments and the experimental challenges. This includes optimizing interferometer designs as well as understanding the role of decoherence. The high sensitivity of matter wave interference experiments to external perturbations is demonstrated to be useful for accurately measuring internal properties of delocalized nanoparticles. We conclude by investigating the prospects for probing the quantum superposition principle in the limit of high particle mass and complexity.Comment: 19 pages, 13 figures; v2: corresponds to published versio