Seminars and public talk listing

Thursday, October 12, 5:05 PM The backb...

Thursday, October 12, 5:05 PM The backbiting problem in polymer synthesis and perspectives on fuel cell molecular modeling Sule Atahan and Michael Wan OPEN
Sule will talk to us about her proposal to study fuel-cell polymers using molecular modelling techniques. Michael will report on his work on the backbiting problem.

Tuesday, October 3rd, 4
Tuesday, October 3rd, 4.00 PM Al�n Aspuru-Guzik What is quantum Monte Carlo? OPEN.
In this talk, I will review the quantum Monte Carlo method for electronic structure. This starts a lecture-group meeting structure where we will try to have a topic review session every month or so by different group members.

Thursday, September 27th, 5
Thursday, September 27th, 5.30 PM Ken Brown, Assistant Professor of Chemistry and Computer Science, Georgia Tech)
OPEN
Limitations of Quantum Simulation Examined by Simulating a Pairing Hamiltonian using Nuclear Magnetic Resonance.

Quantum simulation uses a well-known quantum system to predict the behavior of another quantum system. Certain limitations in this technique arise, however, when applied to specific problems, as we demonstrate with a theoretical and experimental study of an algorithm to find the low-lying spectrum of a Hamiltonian. While the number of elementary quantum gates does scale polynomially with the size of the system, it increases inversely to the desired error bound, epsilon.
Making such simulations robust to decoherence using fault-tolerance constructs requires an additional factor of 1/epsilon gates. These constraints are illustrated by using a three qubit nuclear magnetic resonance system to simulate a pairing Hamiltonian, following the algorithm proposed by Wu, Byrd, and Lidar.

Thursday, September 21st, 5
Thursday, September 21st, 5.30 PM Ivan Tubert-Brohman
Quantum Computing for Biological Applications. For group eyes only. CLOSED .

Friday, September 15, 10
Friday, September 15, 10.300 AM Room M114 CLOSED (but open for prospective students).
James D. Whitfield , Harvard University
End of summer status report on phase estimation research
For group eyes only.

Friday, September 1st, 10:00 AM Room M114 <...
Friday, September 1st, 10:00 AM Room M114 OPEN
Dr. Sergio Granados, U. Mass Amherst
Designing new proton conducting membranes for high temperature and low relative humidity fuel cells, a search for the key factors affecting proton transport in anhydrous conditions.

The widespread utilization of polymer electrolyte membrane fuel cells (PEMFC's) as non-polluting power sources for vehicles and portable electronic devices requires the generation of better performing, more cost effective materials. Our current efforts focus on the development of new proton conductive membranes promoting ionic transport under anhydrous conditions over a range temperature spanning 20C to 150C. The newly synthesized membranes were designed to maximize ion mobility within the polymer matrix and increase the ease of proton dissociation from the proton carrier motifs. The resulting membranes showed improved proton conductivity compared to materials previously reported, particularly at temperatures below 80 C. The effect of other factors such as proton carrier size, electronic structure and supramolecular architecture within the polymer matrix are currently being explored and will be used to further improve proton conductivity.

Jeanette Cramer
UMass Amherst

Investigation of backbiting reactions during ring-opening metathesis polymerizations for the synthesis of polymer electrolyte membranes for fuel cell applications.

Investigations are underway concerning the facile fabrication of polymer electrolyte membranes for fuel cell applications. Of particular interest are block copolymers which contain one conducting block and one
block which provides mechanical and chemical stability to the membrane. One such method for the synthesis of these block copolymers is through Ring-Opening Metathesis Polymerization with functional group
tolerant Grubbs' catalysts. At high monomer to catalyst ratios, this pathway produces high molecular weight polymers with low polydispersities in nearly living like conditions; However, at lower monomer to catalyst ratios, backbiting reactions have been observed. The mechanisms and kinetics of these backbiting reactions have been explored through
Kinetics, Diffusion, and other 2D NMR experiments.

Friday, August 25th, 4:00 PM, Room M114 - <...
Friday, August 25th, 4:00 PM, Room M114 - OPEN
Masoud Mohseni (University of Toronto and University of Southern California)
Direct Characterization of Quantum Dynamics
The characterization of quantum dynamics is a fundamental task in
quantum mechanics, that can be accomplished via quantum process
tomography (QPT). We present a general theory for direct and complete
characterization of quantum dynamics of an open quantum system. In
contrast to all known QPT schemes, our method relies on
error-detection techniques and does not require any quantum state
tomography. By analysis of the number of necessary experimental
configurations and quantum operations in a given Hilbert space, we
demonstrate that our approach is more efficient than all existing QPT
schemes. We also provide a discussion of its possible physical
realizations and illustrate its advantage in partial characterization
of quantum dynamics. Specifically, we demonstrate that our scheme can
be efficiently used for Hamiltonian identification, and also for
simultaneous determination of both the relaxation time T1 and
dephasing time T2.

Wednesday, August 9th, 2006, 2
Wednesday, August 9th, 2006, 2.00 PM Room M114 - OPEN
Clarice Demarchi Aiello (University of Cambridge, now Innsbruck)
Photonic bandgap devices for quantum information processing
We review the applications in the field of solid-state-based Cavity QED of photonic
structures with embedded quantum dots as emitters. We then report on the designed photonic microcavities; the coupling of the cavity modes to the self-assembled dots is discussed. Finally, the experimental efforts towards the fabrication of the device are considered.

Monday, August 7th, 2006, 2
Monday, August 7th, 2006, 2.00 PM Room M114 - OPEN
Sule Atahan (University of Maryland)
Potential energy surfaces and reaction dynamics studies of small triatomic systems: OH+H, OH+D and O+H2
The interaction of open-shell atoms are complicated by the existence of multiple potential energy surfaces and coupling of various angular momenta. The isotope exchange reaction OH+D-> OD+H and the vibrational relaxation of OH radical in collisions with hydrogen atom both involve complex formation. For these radical-radical collisions, the scattering calculations are expensive because of substantially deeper wells corresponding to the complex formation which complicates the exact quantum mechanical study of those reactions due to large basis sets and nonadiabatic effects. We employed and extended the statistical couple channel method of Rackham and Manolopoulos to study vibrational relaxation in complex forming reactions. With our method, it is possible to investigate the relative efficiency of vibrational relaxation during collisions that do not penetrate the complex as compared to vibrational relaxation by redistribution of energy within the complex quantitatively.
In addition, we investigate the potential energy surfaces describing the OH2 van der Waals complex by ab initio methods.

Wednesday July 26, 6.30 PM, Room M114 OPEN
Federico Mena Quintero (GNOME Project, Novell Inc.)
How to make programs fast.

Did the NSF just give you a ridiculously powerful machine, but your programs still run slowly? Do you want to exploit your machine's capabilities? Learn which are the most common causes for program slowness, how to find them, and how to fix them.

Federico has been working for a year on improving the performance of the free software GNOME desktop. He's one of the founders of the GNOME project, and used to be the maintainer of the GIMP image manipulation program. Federico likes good spicy food and has never painted a cow statue.

Seminars and public talk listing

Thursday, October 12, 5:05 PM The backb...

Tuesday, October 3rd, 4

Thursday, September 27th, 5

Thursday, September 21st, 5

Friday, September 15, 10

Friday, September 1st, 10:00 AM Room M114 <...

Friday, August 25th, 4:00 PM, Room M114 - <...

Wednesday, August 9th, 2006, 2

Monday, August 7th, 2006, 2