USC Physics and Astronomy

DEPARTMENT COLLOQUIUM

The Department of Physics and Astronomy Colloquium is held on Monday afternoons at 4:15 pm in room SLH 102 unless otherwise noted. Refreshments are served at 4:00 pm.

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Spring 2012

January 9
Emerging Quantum Optical Networks
Joseph Kerckhoff
NIST & University of Colorado

View Abstract

Economic and environmental pressures continually push information systems smaller and to operate at lower energies. As a consequence, optical technologies are increasingly utilized to connect computing devices over short distances. For similar reasons and in view of recent advances in nanophotincs, large scale electro-optical integration in processors could also be advantageous. These trends raise some fundamental hardware questions however. For example, the energy equivalent of today’s CMOS logic operation is a countable number of photons. How could we control a physical optical "bit" with significant quantum noise? Can the full quantum complexity and emergent behavior of an optical network be engineered? The stability problem is illustrated by a recent experiment in which quantum fluctuations destabilize bistability (a canonical context for digital logic) in an ultra-low energy, highly non-linear optical device. On the other hand, the emergence of a new binary switching phenomena in this device is also compelling. I will discuss a proposal for stabilizing related devices with a simple, on-chip and alloptical feedback network, utilizing a nascent theory of quantum optical circuits that resembles a noncommutative generalization of electrical circuit theory. Finally, I will describe a potential all-optical feedback network capable of stabilizing an unknown quantum superposition state without external oversight or even a regulating "clock", demonstrating the wide scope of quantum optical control.

January 16
Martin Luther King Jr. Holiday

January 23
Strong Light-Matter Interactions in Semiconductor Quantum Dots Coupled to Photonic Crystals
Edo Waks
Nanophotonics Group
Electrical & Computer Engineering
University of Maryland

View Abstract

Two dimensional photonic crystals have been recognized as a highly promising scalable platform for compact integrated photonics. Another important aspect of photonic crystals is their ability to localize and trap light to spatial volumes on the order of a cubic wavelength, resulting in extremely high electromagnetic intensities. Recently, it has been shown that by embedding a single quantum dot (QD) in the high field region of photonic crystal cavities it becomes possible to achieve strong light-matter interactions at the single photon/single atom level. These unprecedented interaction strengths open up the possibility for creating nonlinear optical effects approaching the single photon level. In addition, they can be exploited to engineer unique quantum mechanically entangled states of light and matter that enable scalable quantum networks. In this talk, I will discuss our work on coupling indium arsenide (InAs) QDs to photonic crystal structures for creating nonlinear optical interactions at low photon numbers, and for storing and transferring quantum information from QD spin to photons for quantum networking. I will describe an experimental demonstration of giant optical Stark shifts with only 10 photons of energy by using a strongly coupled cavity-QD system, as well as a recent demonstration of alloptical switching with only 150 photons of control energy. I will then describe our work on coupling QD spin to light in order to realize a quantum transistor that can exhibit the quantum mechanical property of entanglement. The quantum transistor could enable a novel class of opto-electronic devices that serve as a fundamental building block for quantum computers and quantum networks.

January 30
Today's colloquium by Richard G. Harris, D-Wave Systems has been rescheduled to February 13.

February 6
The Origin of the Universe and the Arrow of Time
Sean Carroll
Senior Research Associate
Moore Center for Theoretical Cosmology and Astrophysics
Physics Department
California Institute of Technology

View Abstract

Over a century ago, Boltzmann and others provided a microscopic understanding for the tendency of entropy to increase. But this understanding relies ultimately on an empirical fact about cosmology: the early universe had a very low entropy. Why was it like that? Cosmologists aspire to provide a dynamical explanation for the observed state of the universe, but have had very little to say about the dramatic asymmetry between early times and late times. I will discuss whether the problem of low-entropy initial conditions can be alleviated within the context of a multiverse.

February 13
Introduction to D-Wave One Processor
Richard G. Harris
D Wave Systems, Inc.

View Abstract

The D Wave One is a prototype computing platform that harnesses a physical process referred to as quantum annealing. The technology is built on a superconducting chip composed of analog devices that enable a quantum annealing algorithm and digital components that apply programmable on-chip flux biases. This lecture will provide a high level introduction to the D-Wave One processor architecture and a discussion of the promises and challenges that have been encountered. I will conclude with a brief glimpse of a second generation processor currently in development.

February 20
President's Day Holiday

February 27
TBA
Prof. Venkatesh Narayanamurti
The Narayanamurti Group
Department of Physics
Harvard University

March 5
TBA
Tommaso Roscilde
Assistant Professor
Laboratoire de Physique
Ecole Normale Superierure de Lyon
France

March 19
TBA

March 26
Dr. Gary Grest
Scientist
Center for Integrated Nanotechnologies
Sandia National Lab

April 2
TBA
Sergio Boixo
Information Sciences Institute
USC

April 9
TBA
Samantha J. Butler
Neuroscience
USC

April 16
TBA
David Beratan
Beratan Research Group
Chemistry
Duke University

April 23
TBA
Myron F. Goodman
Biological Sciences and Chemistry
USC