Physics and Engineering Physics

Seminar on Control of Quantum Systems

November 9, 2011

Speaker: Dr. Juha Javanainen, University of Connecticut Title: Bose-Einstein condensate in a double-well trap: back-action from measurements of atom numbers forces classical behavior. Abstract: We consider a double-well trap containing a BEC, assuming that the numbers of the atoms on both sides of the trap are monitored continuously using light scattering. We develop both an exact quantum mechanical simulation, including back-action from detection of the scattered light, and a classical simulation by expanding the quantum theory as powers in the inverse of the total number of condensate atoms. In our numerical examples the quantum and classical descriptions give results so similar that [Read more...]

Seminar on Control of Quantum Systems

November 2, 2011

Speaker: Prof. Andre Bandrauk, University of Sherbrooke Title: Movie with lasers: Molecular optical visualization - imaging of electrons Abstract: Studying and using light or 'photons' to image and then control and transmit molecular information is among the most challenging and significant research fields to emerge in recent years and appropriately called "Molecular Photonics". One of the latest growing areas involves research in the temporal imaging of quantum phenomena, ranging from molecular dynamics in the femto-time regime for atomic rearrangements to the attosecond time scale of electron motion. In fact the attosecond "revolution", the result of "evolution" of ultrafast laser technology, is now [Read more...]

Seminar on Control of Quantum Systems

October 26, 2011

Speaker: Prof. Elizabeth McCormack, Bryn Mawr College Title: Probing Long-Range Configurations of Molecular Hydrogen Abstract: Very long-range molecular configurations are of interest in a variety of contexts, for example, in the astro-chemistry of cold molecular clouds and in planetary atmospheres, including our own. Such states can be more than 10 times the size of the ground state and often possess energies above multiple ionization potentials and dissociation limits resulting in diverse and complex decay dynamics. Many of these configurations possess a double-well character arising from the interaction of molecular Rydberg states, repulsive doubly-excited states, and ionic states. The ion pair in hydrogen, [Read more...]

Seminar on Control of Quantum Systems

September 28, 2011

Speaker: Prof. Alexei Sokolov, Texas A&M University Title: Controlled femtosecond laser filaments for remote sensing Abstract: Femtosecond laser filamentation starts when Kerr-induced self-focusing overcomes beam diffraction. When a threshold power is reached, the transverse intensity profile of the laser beam decreases until nonlinear defocusing mechanisms come into play, due to for example production of plasma or multiphoton excitation of conduction-band electrons. The balance between self-phocusing and defocusing processes results in formation of a filament that can propagate over distances orders of magnitude longer than the Rayleigh range corresponding to their transverse dimensions. In a recent experiment we have used filaments for sub-diffraction-limited [Read more...]

Seminar on Control of Quantum Systems

September 14, 2011

Speaker: Prof. Christopher Monroe, Joint Quantum Institute and University of Maryland Title: Quantum simulation of magnetism with individual atomic qubits Abstract: Trapped atomic ions are among the most promising candidates for quantum information hardware, with entangling quantum gates available through state-dependent laser forces applied to individual ions in a Coulomb crystal. When such a laser force is applied globally, an effective spin-spin interaction emerges whose sign and range can be precisely controlled with the laser, and any possible spin correlation function can be measured with standard state-dependent fluorescence techniques. This allows the quantum simulation of interesting spin models that possess nontrivial ground [Read more...]

CQS Seminar: Grapheotonics - Photonics with CNTs

December 1, 2010

Speaker: Prof. Stefan Strauf, Stevens Institute of TechnologyTitle: Grapheotonics: Photonics with CNTs and GrapheneAbstract: Carbon allotropes such as carbon nanotubes (CNTs) and graphene are well known for their outstanding electronic, thermal, and mechanical properties and have recently also gained tremendous interest as a nanomaterial for photonics and quantum photonics devices. In this talk we will review some of our recent work: Blinking and spectral diffusion are hallmarks of nanoscale light emitters. We demonstrate suppression of blinking in individual CNTs by manipulation of their dielectric environment, resulting in five-fold enhanced exciton emission. For exfoliated graphene we show how Raman spectroscopy [Read more...]

Patrolling the Quantum - Classical Border

November 18, 2010

Speaker: Prof. Joseph H. Eberly, University of RochesterTitle: Patrolling the Quantum-Classical Border: Bell Inequalities and Intense-Laser Control of AtomsAbstract: An exciting frontier in physics is the border between quantum and classical physics. In fact, no one can define precisely where the border is. This is one thing that makes recent reinforcing combinations of experiment and theory in areas of optics attractive. In the talk I will expose open questions about the quantum-classical border location in two very different contexts. [Read more...]

Controlling Light in Photonic Nanostructures

November 17, 2010

Chee Wei Wong, Columbia University [Read more...]

CQS Seminar: Assemblies of Metal Nanoparticles for SERS-based Chemical Sensing

November 17, 2010

Speaker: Prof. Svetlana Sukhishvili, Stevens Institute of TechnologyTitle: Assemblies of Metal Nanoparticles for SERS-based Chemical SensingAbstract: I will summarize work we have been doing at Stevens on the development of SERS-active substrates and photonic cristal fibers, and discuss challenges and opportunities in SERS-based sensing. Specific topics will inculde assembly of silver and gold nanoparticles and nanoshells for optimized SERS enhancement, understanding contributions of electromagnetic and chemical mechanisms in SERS, and controlling molecular binding with nanoparticles. I will also discuss prospective applications of our detection platforms for ultra-sensitive detection of a variety of functional molecules using SERS. Our research has been [Read more...]

CQS Seminar: Mid-IR Ultrafast Diagnostic Instrumentation for the Measurements of Carrier Dynamics in Quantum Cascade Lasers

November 3, 2010

Speaker: Dr. Elaine Lalanne, Center for Advanced Studies in Photonics Research, University of Maryland, Baltimore CountyTitle: Mid-IR Ultrafast Diagnostic Instrumentation for the Measurements of Carrier Dynamics in Quantum Cascade Lasers Abstract: We have developed an integrated laboratory Mid-IR ultrafast diagnostic instrument to investigate ultrafast electronic and radiative processes in Quantum Cascade Lasers (QCLs) and related semiconductor structures. This instrumentation is needed to understand the physical processes, improve the fabrication and optimize the performance of room temperature QCLs and the semiconductor structures. Preliminary pump-probe results utilizing 120 fs, 4.8µm, 250-kHz, Mid-IR pulses will be discussed. The measurement provides information about the [Read more...]

CQS Seminar: Following quantum coherence evolution of open systems

October 13, 2010

Speaker: Prof. Ting Yu, Stevens Institute of TechnologyTitle: Following quantum coherence evolution of open systemsAbstract: Quantum coherence dynamics of open systems is a generic paradigm that has been widely discussed in research fields ranging from atomic and optical physics to condensed matter physics and to quantum information science. Among current research frontiers are non-Markovian theory and disentanglement. In this talk I will present highlights of our work on several key issues in entanglement dynamics and non-Markovian quantum systems including evolution of spin entanglement under phonon noise, non-Markovian state diffusion and fast-tracking of entanglement. [Read more...]

CQS Seminar: Ultrafast control of Raman transitions

October 6, 2010

Speaker: Prof. Svetlana Malinovskaya, Stevens Institute of TechnologyTitle: Ultrafast control of Raman transitions: from noninvasive imaging to molecular coolingAbstract: Advances in laser technology stimulate the study of control of molecular dynamics. Applications are diverse and include the development of novel imaging techniques based on coherent anti-Stokes Raman scattering (CARS), which aims to reveal molecular specific structures. We will discuss novel methods in CARS microscopy which make use of femtosecond laser pulses in combination with quantum control methods. Another application is the implementation of an optical frequency comb for internal state cooling from Feshbach molecules. Optical frequency combs are being recognized [Read more...]

CQS Seminar: Ultralong-range and ultracold Rydberg molecules

September 22, 2010

Speaker: Dr. H. R. Sadeghpour, ITAMP, Harvard-Smithsonian Center for AstrophysicsTitle: Ultralong-range and ultracold Rydberg molecules: a new molecular bondingAbstract: How Rydberg atoms are perturbed in the presence of ground state atoms is an old subject. In this talk, I describe several exotic classes of ultralong and ultracold Rydberg molecules, bound by a "Rydberg" bond, and with fascinating properties. A subset of these molecules have recently been realized in the lab and are by far the largest molecules ever created. I will discuss a new set of ulralong Rydberg molecules formed due to the interaction of Rydberg atoms and polar molecules [Read more...]

CQS Seminar: Ultracold Atoms: from Precision Metrology to Dark Matter

September 15, 2010

Speaker: Prof. Tanya Zelevinsky, Columbia UniversityTitle: Ultracold Atoms: from Precision Metrology to Dark MatterAbstract: We will discuss recent and ongoing precision measurements with laser-cooled atoms in optical lattices. A sub-hertz characterizationof the optical atomic lattice clock will be presented, as well asprogress toward ultracold molecules and a molecular lattice clock. We will also describe the applications of our AMO physics research tofundamental physics questions such as dark matter and stability of theconstants of nature. [Read more...]

CQS Seminar: Strong field physics reveal through time-domain spectroscopy

November 18, 2009

Speaker: Prof. George Gibson, University of ConnecticutTitle: Strong field physics revealed through time-domain spectroscopyAbstract: Pump-probe spectroscopy is generally used to study molecular dynamics. Over the past few years, we have turned this around and used molecular dynamics to study strong field interactions with molecules, using time-domain pump-probe spectroscopy. Many stromg field experiments are insensitive to the final state of the atom or molecule under study, although the final state contains important information about the strong field interaction. By studing the vibrational dynamics of the final state we can learn about interaction of the strong laser field with a molecule. In this talk, I will review a number of our results, including the meacurement of [Read more...]

CQS Seminar: How did Pauli Miss It

October 26, 2009

Speaker: Prof. David J. Tannor, Weizmann Institute of Science Title: How did Pauli Miss It: An Exact Formulation of Quantum Mechanics with Complex TrajectoriesAbstract: Ever since the advent of Quantum Mechanics, there has been a quest for a trajectory based formulation of quantum theory that is exact. In the 1950's, David Bohm, buiding on earlier work of Madelung and de Broglie, developed an exact formulation of quantum mechanics in which trajectories evolve in the presence of the usual Newtonian force plus an additional quantum force. In recent years, there has been a resurgence of interest in Bohmian Mechanics as a [Read more...]

CQS Seminar: Exotic electronic states in semiconductor quantum dots

October 21, 2009

Speaker: Sokratis KalliakosTitle: Exotic electronic states in semiconductor quantum dotsAbstract: Quantum correlations among electrons confined in semiconductor quantum dots (QDs) are expected to lead to exotic states of matter, such as an electron molecule. In the limit of vanishing electron density, the distances between confined electrons are rigidly fixed like those of nuclei in conventional molecules. The electronic excitations of such a molecule are quantized normal modes of roto-vibration, whose quanta have either a rigid-rotor or relative-motion character. I will present a joint experimental and theoretical investigation of the neutral electronic excitations of nanofabricated AlGaAs/GaAs QDs that contain four electrons. [Read more...]

CQS Seminar: Optimally Controlled Vibrational Population Transfer in a Diatomic Quantum System

September 30, 2009

Speaker: Dr. Praveen Kumar, Stevens Institute of TechnologyTitle: Optimally Controlled Vibrational Population Transfer in a Diatomic Quantum SystemAbstract: Optimal control theory is used to investigate controlled vibrational population transfer in a diatomic quantum system. The problem of finding the optimal laser field, needed to achieve a specific quantum transition from an initial state to the desired target state, is investigated using an iterative method and the conjugate gradient method. The time-dependent Schroedinger equation is solved, that describes the interaction of laser radiation with matter within the dipole approximation. The control objective is chosen as the value of transition probability from [Read more...]

CQS Seminar: Using Quantum Mechanics to Detect Anthrax

September 9, 2009

Speaker: Prof. Marlan O. Scully, Texas A&M University and Princeton UniversityTitle: Using Quantum Mechanics to Detect AnthraxAbstract: Counterintuitive effects such as amplification without noise are lasing without inversion are examples of quantum coherence. More recently, the study of quantum coherence effects has lead to improvements in laser spectroscopy which allow us to 'instantaneously' detect anthrax type endospores [1,2]. In the latter example, marker molecules in the endospore are put into maximal oscillation which is detected by scattering laser light off the coherently oscillating molecules. This is called coherent Raman scattering and is type of Dicke superradiance. The preceding topics were [Read more...]

CQS Seminar: Optimally Controlling Osteoarthritis and Tumors with Spin 3/2

September 2, 2009

Speaker: Prof. Alexej Jerschow, New York UniversityTitle: Optimally Controlling Osteoarthritis and Tumors with Spin 3/2Abstract: Magnetic resonance imaging (MRI) is a powerful noninvasive diagnostic method for obtaining images from human body. 23Na (S=3/2) MRI has been used for a variety of tissue and organ imaging, including the brain, cartilage, disc, breast, and kidney. With the advent of high-field MRI scanners high-resolution images can be obtained within clinically acceptable scan times. In cartilage and intervertebral disc (IVD) tissue the sodium concentration is particularly high and has been shown to be indicative of early degenerative changes. Current limitations of this methodology are [Read more...]