Physics and Engineering Physics

Control of Quantum Systems Seminar

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...]

Control of Quantum Systems Seminar

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...]

Control of Quantum Systems Seminar

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...]

Control of Quantum Systems Seminar

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...]

Control of Quantum Systems Seminar

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...]

Control of Quantum Systems Seminar

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...]

Coherent light-matter interactions: shedding a new light on semiconductors

March 4, 2009

Speaker: Prof. Alan D. Bristow, JILA, University of Colorado & NIST Coherent light-matter interactions in semiconductors are essential to future communications and optoelectronics technologies. Semiconductors and their nanostructures provide a link between light and electrons. [Read more...]

Control of Quantum Systems Seminar

December 3, 2008

Speaker: Prof. Kate Kirby, ITAMP at Harvard-Smithsonian Center for Astrophysics and Harvard University Title: Atomic and Molecular Physics for Forefront Astronomy Abstract: Across a wide range of wavelengths and encompassing a rich menagerie of astrophysical objects and environments, the need for atomic and molecular data to advance forefront astronomical research has never been greater. Over the last decade, astronomical discoveries, such as the detection of brown dwarfs and extra-solar planets, and the observation of new phenomena, such as x-rays from comets, have created a demand for more and different kinds of data. The next generation [Read more...]

Control of Quantum Systems Seminar

November 19, 2008

Speaker: Prof. Jennifer P. Ogilvie, Department of Physics, University of MichiganTitle: Advances in nonlinear spectroscopy: applications in imaging and studies of condensed phase dynamicsAbstract: Nonlinear spectroscopies provide powerful tools for probing biological systems. This talk will discuss applications of different nonlinear spectroscopies for imaging and condensed phase studies. For biological imaging, Coherent anti-Stokes Raman scattering (CARS) offers the advantage of providing endogenous contrast based on the inherent vibrations of different chemical species. We present a time-domain Fourier transform-based method that produces spectrally resolved CARS images over the considerable bandwidth of a broadband laser source, and discuss recent results in [Read more...]

Control of Quantum Systems Seminar

November 5, 2008

Speaker: Prof. Mark Hillery, Department of Physics, Hunter College of CUNYTitle: Quantum MachinesAbstract: We discuss quantum information processing machines. We start with single purpose machines that either redistribute quantum information or identify quantum states. We then move on to machines that can perform a number of functions, and which function they perform is determined by a program, which is itself a quantum state. Examples of both deterministic and probabilistic programmable machines are given, and we conclude with a discussion of the utility of quantum programs. [Read more...]

Control of Quantum Systems Seminar

October 15, 2008

Speaker: Prof. Irina Novikova, Department of Physics, College of William & Mary Title: Optimal quantum memory with atomic ensemblesAbstract: Efficient and reliable quantum communication will require the control of individual photons. As a step toward this objective, we have demonstrated promising techniques that involve using a dynamic form of electromagnetically induced transparency to optimally and reversibly map arbitrary pulses of light onto an ensemble of warm Rubidium atoms. Our techniques, demonstrated in atomic vapor, are applicable to a wide range of systems and protocols. [Read more...]

Control of Quantum Systems Seminar

October 1, 2008

Speaker: Prof. Georg Raitel, Department of Physics, University of Michigan Title: Bose-Einstein condensates in a one-dimensional optical lattice Abstract: Our recent work on the dynamics on BECs in combinations of one-dimensional optical lattices and magnetic traps will be described. I will first review some experimental methods used. In experiments wil shallow lattices (depth about one recoil energy), we have implemented an atom cavity. On one side, atoms trapped in the cavity are confined by the magnetic potential, while on the other, the atoms are Bragg-reflected by the optical lattice. We have demonstrated the cavity by recording the momentum-space Bloch [Read more...]

Control of Quantum Systems Seminar

September 10, 2008

Speaker: Prof. Christopher Monroe, Joint Quantum Institute, University of Maryland and NISTTitle: Quantum Networks of AtomsAbstract: Trapped atomic ions are among the most promising candidates for a future quantum information processor, with each ion storing a single quantum bit (qubit) of information. 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. The conventional approach to forming entangled states of multiple trapped ion qubits is through the local Coulomb interaction accompanied by appropriate state-dependent optical forces. Recently, trapped ion qubits have been [Read more...]

Quantum chaos in a non-compact cusp

May 3, 2007

I will review some basic concepts of Semiclassical Quantum Chaos (Quantization, Wigner Distribution, Quantum Ergodicity, etc.) and show how they apply to the case of the planar billiard Q delimited by the positive x-semiaxis, the positive y-semiaxis, and the graph of f(x) = (x+1)^(-2). We will see that a commonly accepted definition of Quantum Ergodicity (the Schnirelman Theorem) applies, but it does not make much sense from a physical point of view. This is due to a curious anti-tunnel effect that occurs in non-compact cusps. [Read more...]

Recent Developments in the Coherent Control of Molecular Processes

November 29, 2006

Coherent Control affords a means of controlling atomic and molecular processes by manipulating quantum interference terms arising from multiple pathways to the desired final state. The essential principles of coherent control will be reviewed, followed by a selection of recent thepretical developments, such as control of bound state processes via overlapping resonances, classical vs. quantum controlled symmetry breaking, control of penning vs. associative ionization, and entanglement and control in collisional processes. [Read more...]

Quantum computation using single and ensemble polar molecules

November 15, 2006

The dipolar interaction enabling 2-qubit gates is what makes polar molecules different from atoms. I will outline the ideas used for "dipolar switching" with single-molecule qubits. In addition, it is possible to accomplish collective qubits in a gas of polar molecules, and and I'll show how this can be used as a "CPU" for photon qubits. [Read more...]

Interaction-Induced Adiabatic Quantum Pumping of Spin-Singlets

November 8, 2006

Abstract: After a brief introduction to the Landauer description of carrier transport in mesoscopic physics, I will review the mechanism of adiabatic quantum pumping of electrons through nanoscale structures and discuss its analogies with geometric phase. I will then apply the idea of quantum pumping to dynamically generate and control the flow of spin-entangled electrons, each electron belonging to a spin singlet, by means of periodic time variation of localized two-body interactions. This requires a generalization of the theory of quantum pumping since traditional methods based on 1D scattering matrices cannot be applied here. I [Read more...]

Attosecond double-slit experiment

November 1, 2006

A novel application of intense few-cycle laser pulses is demonstrated. Taking advantage of the unique properties of phase- controlled few-cycle pulses, a close analogue of the double-slit scheme has been realized in the time domain. It is distinguished from conventional schemes by a combination of characteristics: (i) The double slit is realized not in position-momentum but in time-energy domain. (ii) The role of the slits is played by windows in time of attosecond duration. (iii) These ``slits'' can be opened or closed by changing the temporal evolution of the field of a few-cycle laser pulse. (iv) At [Read more...]

Quantum Algorithms

October 25, 2006

A review of algorithms for quantum computers. Shor's algorithm for factoring integers in polynomial time and Grover's search algorithm, which affords a quadratic speedup over classical search algorithms, will be discussed. [Read more...]

Controlling Quantum Dynamics Phenomena with Shaped Laser Pulses Acting as Using Photonic Reagents

October 18, 2006

Since the development of the laser some 40 years ago, a longstanding dream has been to utilize this special source of radiation to manipulate dynamical events at the atomic and molecular scales. Hints that this goal may become a reality began to emerge in the 1990's, due to a confluence of concepts and technologies involving (a) control theory, (b) ultrafast laser sources, (c) laser pulse shaping techniques, and (d) fast pattern recognition algorithms. These concepts and tools have resulted in a high speed instrument configuration capable of adaptively changing the driving laser pulse shapes, approaching the performance of [Read more...]