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About September 2009

This page contains all entries posted to Physics Announcements in September 2009. They are listed from oldest to newest.

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September 2009 Archives

September 3, 2009

PhD Proposal Defense - Hui Chen

Hui successfully defended his PhD proposal on September 3, 2009

TITLE:
The high-order quantum coherence of thermal light

ABSTRACT:
Fifty years ago, Hanbury Brown and Twiss (HBT) discovered a nontrivial intensity‐intensity correlation that the thermal light has a twice chance of being measured by two individual photo‐detectors within its coherence volume. This HBT effect was finally interpreted as intensity fluctuation. However, with careful theoretical and experimental studies, we found that intensity fluctuation faces difficulty. Recently, our theoretical and experimental works have provided some clear evidences. Moreover, we propose a serial of further works, in order to explicitly demonstrate that the HBT effect has to be described quantum mechanically as two‐photon interference.

September 9, 2009

Seminar: Wednesday, September 9, 2009 at 3:30 p.m.

Quantum Networks with Ions, Phonons, and Photons
Dr. Chris Monroe
Joint Quantum Institute, University of Maryland and NIST


Trapped atomic ions are among the most promising candidates for quantum information processing. All of the fundamental quantum operations have been demonstrated on this system, and the central challenge now is how to scale the system to larger numbers of qubits. By entangling atomic qubits through both deterministic phonon and probabilistic photon interfaces, the trapped ion system can be scaled in various ways for applications in quantum communication, quantum computing, and quantum simulations. I will discuss several options and issues for such atomic quantum networks, along with state-of-the-art experimental progress.


Location: Physics Bldg., Room 401

September 16, 2009

Seminar: Wednesday, September 16, 2009 at 3:30 p.m.

Human Restructuring of the Terrestrial Biosphere, Surface Processes and Global Climate
Dr. Erle Ellis
University of Maryland Baltimore County


Humans have been altering terrestrial ecosystems for millennia, beginning with early use of fire for hunting and leading now to the wholesale restructuring of the terrestrial biosphere for use in agriculture and settlements. This presentation will explore the global implications of land use by humans, beginning with the first farmers and then detailing the global ecological patterns created by human activities from the 1700s to the present. Anthropogenic global patterns in ecosystem and land surface processes are likely causing global changes in atmospheric pattern and process- a fruitful pathway for future research.


Location: Physics Bldg., Room 401

September 23, 2009

Seminar: Wednesday, September 23, 2009 at 3:30 p.m.

Er:YAG is a 2.46-level laser
Dr. Jeffrey O. White
Army Research Laboratory

For a high power solid state laser in the 1.6 micron spectral region, Er3+ is a natural choice for the active ion. One advantage is the possibility of low-quantum-defect pumping with diode lasers. A disadvantages is the presence of upconversion. I will discuss recent modeling and experiments on lasing, and z-scan measurements of upconversion. 'Level parameters' will be proposed for quantitative comparison of rare-earth-doped solid-state laser media, operating temperatures, pump and laser wavelengths.


Location: Physics Bldg., Room 401

September 30, 2009

Seminar: Wednesday, September 30, 2009 at 3:30 p.m.

Coherent Control of Electrical Current and Terahertz Radiation
Dr. Ki Yong Kim
University of Maryland College Park

Sandwiched between the traditional optical and microwave regimes, far infrared or terahertz (THz) frequency has recently drawn special attention due to its ubiquitous nature, as well as its potential for molecular sensing, biomedical imaging and spectroscopy, security scanners, and plasma diagnostics. For these applications, there is a present and growing need for high-energy, compact THz sources at a tabletop-scale. In this effort, I will present our recent demonstration of high-energy (>5 microjoule), super-broadband (>75 THz) THz radiation generation using a tabletop femtosecond laser [1]. In this scheme, an ultrafast pulsed laser’s fundamental and second harmonic fields are mixed in a gas of atoms or molecules, causing them to ionize. The resulting plasma can generate a directional electron current and simultaneous far-field THz radiation, all coherently controlled by the laser field amplitudes and relative phase. By controlling the relative phase, we can also switch the output energy between THz and harmonics.


Location: Physics Bldg., room 401

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