Research Interests

Laser cooling and trapping takes place in an Ultra-High Vacuum environment at a pressure of 10-8 torr. The picture shows one of our setups: you can see the UHV vacuum chamber, six magnet coils which cancel the earth's magnetic field, and various optics used to steer the many laser beams required for our experiments. You can click on the picture for a larger view of the chamber, or visit our picture gallery with further images.

The laser cooling and trapping group at the OSC conducts a variety of research to explore the fundamentals of quantum mechanics, and to increase our understanding of the strange quantum mechanical world and our ability to manipulate and control it. In all our work we use laser trapped neutral atoms (see picture above, plus this picture gallery), with special emphasis on a type of laser trap known as an optical lattice. Optical lattices are periodic potentials formed by the atom-light interaction in laser standing waves, and are capable of trapping millions of atoms deep in the quantum regime (optical.pdf, atom.pdf). A great richness of modern physics issues can be studied using laser trapped atoms as a model system, aided by the extraordinary flexibility with which the atom/light interaction can be designed. Over the past few years our research program has come to focus on two closely related areas: (i) the development of techniques for quantum state control and quantum information processing, and (ii) the use of quantum tunneling in mesoscopic quantum systems and the role of decoherence in the transition from quantum mechanics to classical physics. The development of tools to prepare, manipulate and measure the quantum mechanical state of a physical system represents one of the great challenges of modern science. As the miniaturization of computers and data storage systems continue, transistors and other solid state devices are projected to approach atomic size early in the 21st century. At that point they will be manifestly non-classical objects, and the feasibility of quantum control will determine if their quantum properties become a resource or a problem. Motivated in part by fundamental interest and in part by this emerging need to manipulate nature at this most fundamental level, we are using optically trapped atoms to discover new ways of preparing and controlling quantum states (quantum.pdf). As an example we have developed the steps necessary to prepare atomic wavepackets in the pure quantum mechanical ground state of the microtraps in an optical lattice (raman.pdf), and have used these as a starting point for further quantum state manipulation. Very recently the concepts of quantum information and quantum computing have become unifying themes for much of the work being done on quantum state control. In quantum information science a two-level quantum system constitutes a unit of quantum information, a "qubit", and the juxtaposition of many such systems becomes a "quantum register". Controlled time evolution of the quantum register can then be regarded as a "computation", which transforms a given input state into a desired output state according to a "program". It has been shown that a quantum mechanical computer can solve certain classes of problems, such as searching large databases or factorizing large numbers into their prime components, which are intractable on any computer governed by classical mechanics. However, so far two insurmountable problems crop up when one tries to build a quantum computer in the laboratory: the loss of quantum coherence due to interactions between the computer and its surroundings, and the complexity of the control operations required to manipulate it. Together with colleagues at the University of New Mexico (Ivan Deutsch) we have shown that optically trapped neutral atoms offer some unique features that may help solve these problems (logic.pdf). For many years a paradigm for quantum coherent evolution has been the occurrence of tunneling in macroscopic and mesoscopic double-well potentials. In spite of a huge body of work performed in the field a series of fundamental questions remain to be addressed in well-controlled experiments, notably whether coherent evolution can be enforced in the presence of a noisy environment, by suitable perturbations of the state of the tunneling particle. The challenge is here to find simple physical systems, which can be made to interact with a well characterized environment in a controlled manner. We are currently using far-off-resonance optical lattices to create double-well optical potentials for Cesium atoms, and observing coherent quantum tunneling of entire atoms through the optical wavelength-sized barrier separating the potential minima (meso.pdf). To study the process of decoherence in more detail we are also developing a method to measure the entire atomic ground state density matrix.