I'm interested in nonlinear optics, atom optics and optical precision measurements. In nonlinear optics, I study photorefractive systems for measurement and information processing, especially self-organized information processing. Our group is currently investigating acoustic and RF antenna-array signal processing and sensing of chemical vapors. Atom-optics research centers on the development of atom waveguides, atom "chip" technology, and the use of Bose-Einstein condensates to make practical devices. The group is currently developing integrated atom interferometers for inertial navigation and other sensing applications.
My research interests are related to the theoretical analysis and numerical simulation of ultrafast processes in atoms, molecules and clusters interacting with intense laser pulses. Laser systems currently generate light pulses with field strengths exceeding that of the Coulomb field within an atom or molecule. Pulse durations are as short as a few femtoseconds (10-15 sec) or even less in the attosecond regime, which correspond to the time scales of electron and nuclear dynamics in materials. My group pursues theoretical studies on the coherent control of chemical reactions, the observation of correlated electron dynamics in atoms and molecules, the imaging of molecular dynamics, and the propagation of ultrashort intense laser pulses. We often work in close collaboration with experimental groups.
My primary research centers on the theory of collisions between trapped atoms and molecules in a dilute gas at milliKelvin temperatures and below. In this novel energy regime, tiny energy splittings (due, for instance, to magnetic interactions or molecular rotations) dominate the collision dynamics. My goal is to unravel these delicate energy exchanges and assess their response to external electromagnetic fields. More broadly, I'm looking for novel approaches to understanding collective motions of many-body quantum-mechanical systems such as electrons in an atom or semiconductor device or atoms in a Bose-Einstein condensate.
My research interests center around the behavior of extremely cold atomic gases. Recent developments in laser-cooling techniques have made possible new families of experiments at microKelvin temperatures. My group investigates techniques for manipulating cold atoms and studies interactions between trapped alkali atoms at collision energies below one microKelvin. I am best known for producing a Bose-Einstein condensate in a sample of trapped atoms. Most recently I've begun a project to measure the electric dipole moment of the electron, a project designed to investigate the particle physics concept known as "supersymmetry."
My research involves theoretical studies of Bose-Einstein condensation, including (1) the modes of oscillation, (2) the quantitative effect of interactions and loss processes, (3) the behavior of a condensate undergoing evaporative cooling, and (4) the thermodynamics of a small number of atoms. My future research interests include the damping processes of coherent excitations, quantum diffusion of the condensate phase, and new methods for treating quantum kinetic theory. I also investigate quantum optics, in which I study the properties of laser fields and their interaction with matter. My other interests include optical cavities and their interaction with atomic beams and quantum measurement theory.
Agnieszka Jaron-Becker is Associate Research Professor of Physics at the University of Colorado, Boulder, and Associate JILA Fellow. In JILA, she serves as co-director of JILA’s Ultrafast Theory Group, which specializes in theoretical studies of ultrafast processes in atoms, molecules, and nanostructures. These ultrafast processes are induced, observed, and controlled by ultrashort intense laser pulses. The laser frequencies studied range from the far infrared through the optical to the soft x-ray region of the electromagnetic spectrum.
My interests are in molecular biophysics and optics for biotechnology. In one project, we employ femtosecond nonlinear electronic spectroscopy to investigate active-site dynamical asymmetry in heme proteins, protein-ligand interactions, and flexibility and conformational diversity in protein folding. Another area of my research involves selection strategies employing a microfluidic cellular spectroscopy and optical force-switching instrument for improving the photophysical properties of fluorescent proteins and sensors used in biological imaging. I'm also interested in algal biofuels. For this project, we designed a lab-on-a-chip microfluidic system and are using it in studies to accelerate the process of screening genetic libraries of algae and rapidly assessing and optimizing growth conditions. Finally, we're using optical forces to measure cellular elastic properties in microfluidic flows.
My major interest includes the development of new light sources at short wavelengths and their use to study dynamic processes in material and chemical systems. In particular, the recent development of high-energy ultrashort-pulse laser technology (in large part by the research group I co-lead with Professor Murnane) allows generation of coherent extreme-ultraviolet (EUV) and soft-X-ray bursts of femtosecond (10-15 sec) and even attosecond (10-18) duration. (For comparison, the ratio of 1 femtosecond to 1 second is about the same as the ratio of 1 second to 30 million years.) The time scales probed by these light pulses correspond to those of chemical reactions and dynamic processes in semiconductors. Short-pulse EUV and X-ray light provides researchers with a unique tool to dynamically observe specific atoms, leading to a deeper understanding of microscopic mechanisms. Furthermore, the ability to implement a "tabletop X-ray laser" light source makes feasible a number of novel applications, such as ultrahigh resolution imaging of single cells, or of nanotech devices, that are independent of the time-resolved aspect. I am also a founding member of the National Science Foundation Engineering Research Center in Extreme Ultraviolet Science and Technology (http://euverc.colostate.edu/) and co-founder of a successful laser company (www.kmlabs.com).
Our group investigates how to apply the tools of atomic, molecular, and optical physics to the microscopic study of quantum systems. We are interested in fundamental questions, such as, “how does classical physics –- such as statistical mechanics --- emerge from the collective behavior of quantum mechanical systems?” We also ask applied questions, for instance, “Can we develop new tools for the manipulation of individual particles, such as ions or molecules, whose interactions and internal degrees of freedom establish new prospects?” For these studies, we aim to marry the tools of quantum gas microscopy, optical tweezer technology, and high precision spectroscopy, in order to gain single-particle control at fundamental length scales and very small energy scales.
My research interests include quantum coherence in nanoscale electrical circuits (solid-state qubits), dynamics of individual electrons in one-dimensional conductors, and ultrafast quantum-limited charge measurements. Recent advances in nanolithography and cryogenic electronics have made it possible to sense individual electrons as they move through nanometer-sized conductors. My research exploits this ability to detect the quantum superposition of macroscopically distinct states of electrical circuits and to detect the flow of single electrons through molecular wires. My current work addresses the following questions: What are the sources of decoherence in solid-state qubits? How efficiently and how quickly do electrons screen each other in nanoscale circuits? Can a sensor of charge reach quantum-limited sensitivity?
My group studies collisions and reactions of simple cold molecules. Our ultimate goal is to understand the quantum mechanical processes involved in making and breaking a chemical bond. We aim to control the reacting molecules external and internal degrees of freedom in the quantum regime. To accomplish this control, we slow down a supersonically cooled molecular beam using time-varying inhomogeneous electric fields (Stark deceleration). The cold (~100 mK) molecules are then loaded into an electrostatic trap to allow for interactions to be studied for several seconds.
My research centers around the interaction of radiation with ions. I use tunable laser photodetachment to probe electron correlation and to investigate dipole-bound states of negative ions. I use negative-ion photoelectron spectroscopy to determine electron affinities and structures of radicals and metal clusters. I study the transition from gas phase to condensed phase by means of photodissociation and photodetachment of cold cluster ions by using nanosecond and picosecond lasers. I study ultrafast molecular rearrangement dynamics using pump-probe, and photodetachment-photoionization of negative ions.
Nonlinear optics has revolutionized laser science by making it possible to efficiently convert laser light from one wavelength into another. My research exploits the extreme nonlinear optical process of high-harmonic generation, whereby light from an ultrafast laser can be coherently upshifted, resulting in a tabletop laserlike (coherent) light source in the soft x-ray region. The x-ray bursts generated during high-harmonic generation represent the fastest strobe light in existence, fast enough to capture electron dynamics in atoms, molecules, and materials. Exciting applications of attosecond science and technology include capturing and controlling the coupled motions of electrons and atoms in molecules, high-resolution imaging, nanoscale heat transport, and ultrafast element-specific dynamics in magnetic materials.
My research includes quantum-state-resolved laser spectroscopy and dynamics of van der Waals and hydrogen-bonded clusters, time-resolved kinetics of atmospheric radicals, crossed-beam studies of state-to-state inelastic and reactive dynamics, high-resolution laser spectroscopy of jet-cooled radicals and molecular ions, nonlinear frequency generation of narrowband tunable infrared laser sources, vibrationally mediated photochemistry in size/quantum state-selected clusters, alignment phenomena, collision dynamics of gases with thin films, and development of atomic force/scanning-tunneling methods for near-field-scanning optical microscopy (NSOM) of molecules on surfaces.
The biochemical cycle of mechanoenzymes generates a force and a displacement that can be measured at the single-molecule level. The outstanding question is how motor proteins transduce chemical energy into physical motion. To answer this question, we use optical tweezers, a focused laser beam that can manipulate micron-sized beads in solution, allowing measurement of position and force in the nanometer (nm) and piconewton (pN) ranges, respectively. Our research focuses on developing assays and precision instrumentation to measure the properties of single-DNA-based molecular motors. Typically, enzymatic motion along the DNA is measured by anchoring the enzyme to a surface and monitoring the position of an optically trapped bead attached to the DNA's distal end.
My main research interest is quantum systems of interacting atoms, photons, and phonons. I seek to engineer and explore new quantum systems with controlled connections for quantum information and quantum optics. In particular I focus on manipulating single and few ultracold neutral atoms and the quest to control mesoscopic mechanical oscillators in the quantum regime. My experiments draw on, for example, low-loss optical interfaces, high-Q mechanical oscillators, and laser cooling and trapping techniques.
My main research interest is ultracold atoms and molecules loaded in optical lattices, which are periodic trapping potentials created by illuminating the atoms and molecules with laser beams. Atoms in optical lattices are analogous to electrons in solid state crystals. Their big advantage is that these "artificial crystals of light" are perfectly clean and highly controllable. Therefore, they are ideal for exploring a whole range of fundamental phenomena that are extremely difficult — or impossible — to study in traditional condensed matter systems. My goal is to study how to control and manipulate these systems to engineer different quantum phases such as superfluids, insulators, quantum magnets, and topological matter. I plan to use them for understanding the physics of strongly correlated bosonic and fermionic systems and nonequilibrium phenomena. Additionally, I am interested in studying how to generate and manipulate entanglement in quantum systems for use in quantum information processing and precision measurements.
My main research interests are quantum information and quantum computing. I try to identify the fundamental limits that physics places on communication, information processing, and sensing and understand the implications of these limits both in terms of practical technologies and fundamental physics. This involves finding new ways to think about information and computation, and new ideas for analyzing them. I have worked on error correction, quantum channel capacities, additivity questions, characterization of quantum annealers, and mathematical properties of entropy.
My research focuses on understanding the interface between ultracold atoms and quantum optics - an understanding I plan to apply to the field of precision measurement. I am presently devising strategies to reduce the effect of the fundamental quantum noise that arises from Heisenberg's uncertainty relationship as applied to atomic spins. In one project, I work on non-destructively measuring and canceling out the quantum fluctuations in the collective spin state of an ensemble of laser-cooled 87Rb atoms in a high-finesse optical cavity. By learning how to minimize the effect of quantum noise in this type of system, I hope to advance the precise measurements required for atomic clocks and in searches for permanent electric dipole moments in atoms and molecules.
My group is currently working in two different areas: The spectroscopy of mass-selected ions in vacuo and the characterization of supramolecular assemblies and nanocrystals at very high pressures.
In the first area, we combine mass spectrometry with laser spectroscopy to characterize positively and negatively charged ions in a very well-defined chemical environment. Much of the behavior of important molecular species is only known in a condensed phase environment (mostly solutions), where interaction with the solvent changes some of the properties of the solute. In order to unravel the effects of solvent-solute interactions, we want to understand the intrinsic properties of the solute and study them as isolated entities in vacuo. There are two main areas of interest at present:
(A) Reductive activation of CO2 by transition metal catalysts:
The development of efficient routes towards generation of sustainable fuel sources by electrochemical reduction of CO2 is an important goal for catalysis research. So far, solvent effects in catalysis are largely not understood or even characterized. Mass-selected clusters of metal anions with CO2 serve as a model system for the reductive activation of CO2 by a catalyst under complete control of the composition and size of the solvation environment. Vibrational spectroscopy and electronic structure calculations are used to obtain molecular-level information on the interaction of solvent with the catalyst-CO2 complex and their effects on one-electron reduction of CO2. If you would like to read more about this, click here.
(B) Photochemistry and electronic structure of transition metal complexes:
We gain a deeper insight into the electronic and geometric structures, and the inter- and intramolecular forces in transition metal complex ions. The experiments contribute valuable information, e.g., on the electron donation/back-donation in metal- and metaloxide-ligand complexes and electron-binding energies. Another example in this program area is the investigation of the photochemistry of species that are relevant to metal-organic reactions, e.g., the photochemistry of chromate esters, which are important intermediates in the oxidation of alcohols by chromate. If you are interested in this area, you can read more here and here.
Energy flow in molecules
All chemical reactions are governed by the nuclear dynamics of molecules, in other words, their patterns of vibrational motion. Therefore, the way in which vibrational energy flows through, and is redistributed in, molecules after excitation has significant impact on the understanding of chemical reaction dynamics, and for the prospect of coherent control of chemical reactions.
Moreover, characterizing energy flow through nanoscale systems has become a critical issue as technology utilizing the progressively smaller sizes of electronic devices encounters the destruction limit of energy density. We follow a new experimental approach to study the flow of energy as it drains out of a certain vibrational mode and arrives at a well-defined place in a molecule. In this approach, we use model systems where the binding energy of an electron in a negatively charged molecule is less than the energies for certain vibrational transitions. This way, we can follow the flow of energy in a molecule by monitoring electron loss and analyzing the kinetic energy distribution of these electrons with high-resolution photoelectron spectroscopy. If you would like to know more about this topic, you can click here.
Supramolecular chemistry and materials at very high pressures
Nanostructured materials (quantum dots, nanowires, nanocrystals) have led to a large research field in the last few years. While there is a huge body of work on their synthesis, the molecular-level details of their interaction with their chemical environment is largely not explored, as is the size dependence of many of their structural properties. High pressure experiments offer a way to tackle such questions.
At relatively low pressures (a few hundred MPa), only intermolecular distances are varied by the application of pressure. This is much less perturbative than variation of temperature or chemical composition. The behavior of nanocrystals at these low pressures yields information on the properties of the interface between the nanocrystals and their chemical environment, including their protective ligands.
Higher pressures (GPa range) can result in phase changes in the solvent or in the nanocrystals themselves. The former will again lead to a change in the interaction of the nanocrystal with its environment. The latter afford access to new materials with new optical and electronic properties. We use photoluminescence spectroscopy and Raman microspectroscopy to study these phenomena.
Our research group explores the frontiers of light-matter interactions, where novel atomic and molecular matters are prepared in the quantum regime and light fields including both continuous wave and ulrashort pulses are exquisitely controlled. The experimental effort builds on and further advances precision measurement, ultracold atoms and molecules, quantum metrology, and ultrafast science and quantum control. We develop new technologies in the areas of high precision laser spectroscopy, atomic and molecular cooling and trapping, optical frequency metrology, quantum control, and ultrafast lasers; and apply these new technologies for research in fundamental physics.
We investigate ultracold strontium atoms confined in optical lattices for high-accuracy atomic clocks and quantum information science. Precise control of optical frequency combs are applied for sensitive molecular detections, high resolution quantum control, and extreme nonlinear optics to explore new frontiers in spectroscopy. Ultracold molecules are being used for fundamental physics tests, studies of novel control of chemical reactions, and new quantum dynamics in ultracold matter.