My Research Interests
Where does the quantum world end and the classical one begin? Typical macroscopic objects obey the laws of classical mechanics. But, since everything is built out of elementary particles which are decidedly quantum, it is hard to understand why quantum signatures do not persist to large scales. These signatures include tunneling (in which a particle can pass through an energetically “forbidden” region) and superposition states (in which a quantum system can in some sense be in two mutually exclusive states at the same time.) My research interests focus on exploring systems at or near the quantum/classical frontier. In particular, I study the quantum properties of “macroscopic” quantum systems like molecules that have a large magnetic moment and superconducting rings in which the electric current can be in a superposition of clockwise and counterclockwise flow.
Single molecule magnets, which are a few nanometers in size, are some of the smallest bistable magnets. How a magnetic particle reverses its orientation is a question of both fundamental interest and practical importance (e.g. for data storage in hard drives). These magnets can reverse their magnetic moment through a process that involves tunneling through an energy barrier that separates the up and down orientations of the magnet. We are doing several experiments to understand and control the reversal process. For example, we use microwaves to induce macroscopic changes in the magnetization.
I'm also starting up a research project to study the macroscopic quantum behavior of SQUIDs (Superconducting Quantum Interference Devices). These devices are superconducting rings in which the electrons “condense” to act as one collective object. This condensate can be put into a macroscopic superposition state in which billions of electrons “flow both ways at once”, an effect demonstrated by an experiment I did several years ago. In a new set of experiments, we will design and build some novel SQUID devices to explore new quantum effects and to try to understand how these systems lose their “quantumness” to eventually behave like most macroscopic objects, that is, classiscally.