Department of Physics

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Colloquia & Seminars, Spring 2008

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Quantum Mechanics via Wigner functions

Speaker:Prof. William Case
Date: April 18, 2008 (Friday)
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
I will present a tutorial on Wigner functions. As we will see the entire content of quantum mechanics may be expressed in terms of Wigner functions and Weyl transforms. This formulation gives a picture that has much in common with classical mechanics and helps us understand the connection between the two theories..

About the speaker:
Prof. William Case is a Physics Professor at Grinnell College, Iowa. He received his Ph.D. in Theoretical Physics from Syracuse University in 1971, and has been on the faculty at Grinnell College since 1980. Currently, he is in research collaboration with Anton Zeilinger’s group at the University of Vienna..

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Engineering at Illinois: Opportunities for Undergraduate and Graduate Study

Speaker: Prof. Bruce Elliott-Litchfield
Date: April 10, 2008 (Thursday)
Time: 4 p.m.
Room: 202 Currens Hall

Abstract
The College of Engineering at Illinois is large, highly ranked, and overflowing with opportunities for students who want to make an impact in the world. Bruce Elliott-Litchfield will speak and answer questions about transferring into undergraduate engineering programs (2+2 and 3+2) and about graduate study (4+2 and PhD) for WIU students at the University of Illinois at Urbana-Champaign.

About the speaker:
Prof. Bruce Elliott-Litchfield is a Professor and Assistant Dean at the College of Engineering of the University of Illinois at Urbana-Champaign.

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Bringing physics to life: Biological insights from computer simulations

Speaker: James C. Gumbart
Date: Friday, March 28, 2008
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
The applications of physics to biology have been growing for nearly a century. These applications take many forms, spanning theory, modeling and experiment, all of which interact with each other to provide coherent pictures of the functioning of biological systems at the molecular and atomic levels. Modeling for example relies on structural data provided by x-ray crystallography and electron microscopy in order to then simulate the experimentally-derived structures in the computer. In these so-called molecular dynamics (MD) simulations, we can visualize the workings of individual proteins, and larger complexes, down to the atomic level over timescales up to 10 microseconds, currently. Applications of this method to a variety of problems, including the translocation of proteins across membranes, the import of vitamins by bacteria, and the curving of membranes in a photosynthetic unit, among others, will be presented. The future promise of MD simulations, spurred by the upcoming development of petascale supercomputers, will also be discussed.

About the speaker:
James C. Gumbart was a student in the Pre Engineering program and then in Physics at WIU from 1999 to 2003. He graduated summa cum laude as a member of the Honors program and the CAS College Scholar in 2003. He was awarded the Phi Kappa Phi Graduate Fellowship and also the GAANN Fellowship Award as an entering graduate student at the University of Illinois in Physics. He has been doing his Ph.D. research on the transport of proteins in biological systems.

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Trapping and Manipulating Atomic Ions for Quantum Information Processing

Speaker: Prof. James Rabchuk
Date: Friday, March 21, 2008
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
Quantum Mechanics as a branch of physics was developed in the early 1900's in response to difficulties in explaining the interaction between light and matter. It must be said that the consequences of this theory are still being worked out today. One of the most important consequences of Quantum Mechanics currently being investigated is the uniquely quantum phenomenon of entanglement. Entanglement describes the situation in which the properties of two or more "objects" are found to be inextricably linked together in a larger system, so that measurements made on one of the "objects" invariably determine the outcome of measurements made on the other "objects". Crucial to the study of entanglement is the ability to manipulate controllably "objects" which are small enough to display quantum behavior. In this talk I will describe the methods currently being used to work with individual atomic ions, which are recognized as one of the most robust tools for exploring quantum entanglement. I will show how atomic ions can be trapped in free space so that their interactions with light and other matter can be controlled deterministically. I will also describe the theory and experiment that showed how trapped ions might be manipulated in an ion-based quantum circuit for use in quantum information processing.

About the speaker:
Dr. James Rabchuk is a Professor at the Department of Physics at Western Illinois University. His recent research interests include various techniques related to quantum computing using trapped ions.

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Decoherence Suppression in Photonic Quantum Information Processing

Speaker: Dr. Sahin Kaya Ozdemir
Date: Friday, March 7, 2008
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
Quantum information science and quantum optics are among the most active fields in modern physics. Recent theoretical and experimental progress has shown that quantum information processing (QIP) tasks such as quantum communication, quantum key distribution, quantum computing and quantum metrology can be performed using linear optical schemes. A key prerequisite for efficient implementation of these tasks is the noise-free manipulation and distribution of quantum states. However, this is not a trivial task as the quantum states are very fragile and easily decohered due to unavoidable coupling to environment. Thus, decoherence suppression schemes (DSS) to protect quantum states in distribution channels as well as in quantum memories are required. In a general setting of QIP, quantum states are either solitary, entangled or part(s) of a larger multi-partite entangled state. Therefore, DSS, which perform equally well for all quantum states could potentially prove useful in future QIP networks. It has been one of our main activities to search for such DSS, which are feasible and robust, and to implement them using linear optics. In this talk, after a brief overview of theoretical and experimental concepts in QIP with linear optics, I will present the results of our experiments on entanglement distillation and faithful distribution of entangled and solitary quantum states. The results open up an exciting possibility for realistic distributed QIP.

About the speaker:
Dr. Sahin Ozdemir is a senior scientist in the Department of Materials Engineering Science, Osaka University, Japan. He received his Ph.D. degree from Shizuoka University, Japan in 2000, and his M.Sc. and B. Sc. degrees from the Middle East Technical University, Turkey. His research interest is on quantum optics and quantum information science.

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High-Energy Physics Seminar: Implications of CP-Violating Transitions in Hot Quark Matter on Heavy Ion Collisions

Speaker: Dr. Harmen J. Warringa
Date: Tuesday, February 26, 2008
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
Quantum chromodynamics (QCD) contains field configurations which can be characterized by a topological invariant, the winding number Qw. Configurations with nonzero Qw break the charge-parity CP symmetry of QCD. We consider a novel mechanism by which these configurations can separate charge in the presence of a background magnetic field - the "Chiral Magnetic Effect". We argue that sufficiently large magnetic fields are created in heavy ion collisions so that the Chiral Magnetic Effect causes preferential emission of charged particles along the direction of angular momentum. Since separation of charge is CP-odd, any observation of the Chiral Magnetic Effect signals event-by-event CP violation and could provide a clear demonstration of the topological nature of the QCD vacuum. We give an estimate of the effect and conclude that it might be observed experimentally.

About the speaker:
Dr. Harmen J. Warringa is a postdoctoral research associate in the Nuclear Theory group at Brookhaven National Laboratory. He received his Ph.D. degree from Vrije University, Amsterdam in 2006.

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High-Energy Physics Seminar: Color Superconducting Matter in Compact Stars with a Magnetic Field

Speaker: Dr. Harmen J. Warringa
Date: Monday, February 25, 2008
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
It is expected that at very high baryon density and low temperature matter will form a color superconductor. Whereas in an ordinary superconductor the electrons form Cooper pairs, in a color superconductor the pairs consists of quarks. The pairing will give rise to a gap in the excitation spectrum. The sole place in nature where one might find a color superconductor in nature is probably inside the core of compact stars, like the neutron star. Therefore one needs to study the behavior of a color superconductor under compact star conditions. It is known that the magnetic field in a neutron star can be enormous, in a special kind of neutron star called magnetar, it could rise to values of 1015 G. In this talk I will discuss calculations of the effect of the magnetic field on the color superconducting gaps. I will argue that there is almost no Meissner effect, so that the magnetic field can penetrate the color superconductor. The magnetic fields in ordinary neutron stars are probably too small to affect the gaps significantly. However, I will show that under very extreme magnetic fields the gap parameters will show de Haas-van Alphen oscillations. It remains to be seen if these extreme magnetic fields could be realized inside the central layers of compact stars. But if the magnetic fields are large enough, the oscillations of the gap parameters could have interesting effects on the cooling rate of a compact star.

About the speaker:
Dr. Harmen J. Warringa is a postdoctoral research associate in the Nuclear Theory group at Brookhaven National Laboratory. He received his Ph.D. degree from Vrije University, Amsterdam in 2006.

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Electronic Properties of Nanomaterials - An NMR Perspective

Speaker: Dr. P. K. Babu
Date: Thursday, February 21, 2008
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
Nanoscale systems are now attracting worldwide attention and fundamental research in this field is required not only to enhance our understanding but also to tailor their properties for technological applications. Traditionally, nuclear magnetic resonance (NMR) experiments have played a crucial role in elucidating the electronic properties of a variety of bulk materials. Application of NMR to nanoscale systems is also proving to be extremely rewarding. In this talk, I will describe how solid state NMR experiments help us to understand the electronic properties of nanomaterials by discussing the results of two recent NMR studies. The first one deals with the semiconductor to metal transition of Se in Ru-Se composite nanoparticles and the second NMR study provides insights to the nature of defect induced magnetism in a new form of nano-carbon material called carbon nanohorns.

About the speaker:
Dr. P. K. Babu is a Research Scientist at the Department of Chemistry, University of Illinois at Urbana-Champaign. He obtained his Ph.D. from the Indian Institute of Science in 1995. His research focuses on the study of electronic properties of a variety of materials including intermetallic compounds, alloys, magnetic materials, superconductors, fuel cell catalysts and carbon nanohorns.

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High-Energy Physics Seminar: Axial anomaly and magnetism of nuclear and quark matter

Speaker: Prof. Misha Stephanov
Date: Friday, February 15, 2008
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
I shall discuss how baryon-rich matter, which makes neutron stars, responds to strong magnetic fields. I shall point out the effect due to the coupling of the magnetic field to the lightest excitations -- axial Goldstone bosons, such as pi-mesons, via quantum anomaly. As a result magnetic field of sufficiently large magnitude (B~(mpi )2/e) induces a gradient of the Goldstone fields localized on a two-dimensional surface -- a pion domain wall. The opposite is also true: the gradient of an axial Goldstone field would induce a magnetic field. Such gradients may indeed be spontaneously generated in a certain state of QCD matter at very large densities -- Goldstone supercurrent state. The matter in such a state is therefore ferromagnetic. The strength of the fields created by such a mechanism in a typical neutron star can be of order 1014-1015 G, sufficient to explain the magnetic fields of some magnetars.

About the speaker:
Dr. Mikhail Stephanov is an Alfred P. Sloan Fellow and an Associate Professor at the University of Illinois at Chicago. He received his Ph. D. degree from Oxford University in 1994 and his M.S. degree from Moscow State University in 1989. Professor Stephanov is working on the theory of strong interactions and its applications to the physics of neutron stars and heavy ion collisions.

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Quantum coherence and coherent control for multidisciplinary applications

Speaker: Dr. Yanhong Xiao
Date: Monday, February 11, 2008
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
Quantum coherence can render an otherwise opaque medium transparent to light. This is called "Electromagnetically induced transparency" (EIT). I will first present a review of these phenomena, how it can be used to slow and stop light for applications in quantum communications, and how it is used to make smaller-than-wrist-watch atomic clocks. I will then present some of our recent research in these exciting fields. In the end, I will discuss potential applications of quantum coherence and coherent control in imaging and sensing.

About the speaker:
Dr. Yanhong Xiao is a postdoctoral researcher at the Harvard-Smithsonian Center for Astrophysics. She obtained her Ph.D. from Harvard University in Applied Physics in 2004. She has a M.S. degree in Opto-Electronics and a B.S. degree in Electronic Engineering from Tsinghua University, China. She is currently studying the coherent interactions between lasers and atoms for applications in quantum information, atomic frequency standards, spectroscopy and imaging.