Fall 2016

Applications of Adiabatic Quantum Computation in Mathematical Optimization

Speaker(s): 
Pooya Ronagh
Dates: 
Friday, October 28, 2016 - 1:30pm to 3:00pm

Adiabatic quantum computation (AQC) is one of the paradigms of quantum computation that has recently gained great attention by advancements in manufacturing superconducting qubits. In this talk, I will overview the advantages and limitations of quantum annealers and methods of simulation of the behavior of futuristic devices. I will then discuss applicability of AQC in solving integer programming problems using a branch and bound framework implemented on a hybrid of a digital and a quantum processor.

Nanomanufacturing

Speaker(s): 
J. Alexander Liddle
Dates: 
Thursday, October 27, 2016 - 3:30pm to 4:30pm

The term “nanofabrication” encompasses the myriad of techniques that can be used to make nanostructures, but only a small subset can make the transition to economic viability that defines “nanomanufacturing”.  I will discuss how market and technical constraints come into play for a variety of nanoscale products, and illustrate key concepts such as speed, yield, precision, defectivity, and modularity by comparing semiconductor manufacturing with the emerging field of DNA-directed self-assembly.  Finally, I will show how nanofabrication techniques can create the...

Frederick Kaufman Lecture Series Peter Hamm (University of Zurich): It’s All About Water

Ultrafast time-resolved spectroscopy, and in particular its extension to multidimensional techniques, can tell us a lot about solvation dynamics, structural dynamics and energy transfer processes of solution phase molecular systems. I will illustrate applications of these spectroscopies by discussing a couple of quite diverse examples that lie at the interface between Physics, Biology and Chemistry. In different ways, these examples highlight the importance of water as a very special substance. That is, I will start out with the ultrafast structural dynamics of bulk water and concentrated salt solution observed by THz photon echoes (Physics), continue with the catalytic cycle of an artificial photosynthetic system designed for light-driven water splitting (Chemistry), and finally discuss the response of an allosteric protein upon an external perturbation (Biology). Also the latter is in fact dictated by the dynamics of the water solvation layer.

Typical Worlds

Speaker(s): 
Jeffrey Barrett
Dates: 
Friday, October 28, 2016 - 3:30pm to 4:30pm

Hugh Everett III presented pure wave mechanics, sometimes referred to as the many-worlds interpretation, as a solution to the quantum measurement problem. While pure wave mechanics is a deterministic physical theory with no probabilities, Everett sought to show how the theory might be understood as making the standard quantum statistical predictions as appearances to observers who were themselves described by the theory. We will consider his argument and how it depends on a particular notion of branch typicality. We will also consider the relationship between...

Storage at the Threshold: Li-ion Batteries and Beyond

Speaker(s): 
George Crabtree
Dates: 
Friday, October 14, 2016 - 1:00pm to 2:00pm

The high energy density and low cost of lithium-ion batteries have created a revolution in personal electronics through laptops, tablets, smart phones and wearables, permanently changing the way we interact with people and information. We are at the threshold of similar transformations in transportation to electric cars and in the electricity grid to renewable generation, smart grids and distributed energy resources. Many aspects of these transformations require new levels of energy storage performance and cost that are beyond the reach of Li-ion batteries....

Xiaoguang Zhang (University of Florida): Generalized Landauer Formula for Finite Biases

Quantum transport theory yields the celebrated Landauer formula for the conductance of a two-terminal device at zero bias in terms of T(EF,0), the transmission coefficient T(E,V) evaluated at the Fermi energy EF and V=0. For finite biases, one must use the nonequilibrium Green’s function (NEGF) method, which entails substantial difficulties. Instead of NEGF calculations, T(E,0) is often interpreted as representing transport at V=E/e. This practice is seriously flawed. In its stead, we employ quantum transport theory to derive a simple finite-bias analog of the Landauer formula. The new formula expresses the differential conductance dI/dV at a bias V in terms of T(μL,2V)+T(μR,2V) and reduces to the Landauer formula at V=0. This new formula is tested for a benzene molecular junction and a magnetic tunnel junction, and is shown to yield excellent agreement with a full NEGF calculation without the need for a self-consistent calculation of T(E,V). 

CANCELLED: Tailoring Chemical and Optical Properties of 2D Transition Metal Dichalcogenides

Speaker(s): 
Talat S. Rahman
Dates: 
Friday, October 7, 2016 - 9:30am to 10:30am

Single-layer of molybdenum disulfide (MoS2) and other transition metal dichalcogenides (TMDC) appear to be promising materials for next generation applications (optoelectronic and catalysis), because of their low-dimensionality and intrinsic direct band-gap which typically lies in the visible spectrum. Several experimental groups have already reported novel electronic and transport properties which place these materials beyond graphene for device applications. MoS2 is also known to be a leading hydrodesulfurization catalyst. Efforts are underway to further tune...

Modelling Carbon Materials from Pencil and Paper to High-throughput Screening

Speaker(s): 
Johan Carlsson
Dates: 
Thursday, October 20, 2016 - 4:00pm to 5:00pm

Carbon materials have extraordinary properties, but utilizing these properties in applications requires a deep understanding of the materials. Modelling and simulations can here be a very useful complement to experiments and even be used to predict properties ahead of the experiments. This is particularly relevant for graphene, which was investigated theoretically in great detail long before it was possible to perform any experiments. The first investigations were performed on ideal sheets using pencil and paper, but as grown grown graphene sheets are often...

Dipolar Exciton Condensation in One-dimensional Materials

Speaker(s): 
David Abergel
Dates: 
Thursday, December 15, 2016 - 4:00pm to 5:00pm

We demonstrate that spatially separated populations of one-dimensional electrons and holes may form a true condensate of dipolar excitons characterised by off-diagonal long range order and global phase coherence. This is unexpected, since the Mermin-Wagner theorem states that long range order should not exist in 1D systems. 
However, we show that adding a single particle hybridization between the electron and hole populations breaks a continuous symmetry and allows many body effects to dominate the ground state. The superfluid condensate may have...

Potential Inhomogeneities in Presence of Strong Interactions: Birth and Death of Superconductors

Speaker(s): 
Rajdeep Sensarma
Dates: 
Thursday, November 3, 2016 - 4:00pm to 5:00pm

Strong repulsive interactions and potential in homogeneities both tend to localize Fermions on a lattice and lead to loss of superconductivity. The natural question that comes up is whether they compete or complement each other when both are present in a system at the same time. In this talk, we will use a effective Hamiltonian approach which treats both interactions and in homogeneities on the same footing to look at two systems: (a) the Ionic Hubbard Model at half-filling, where a staggered potential on a bipartite lattice competes with interactions to...

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