A long-standing theme of atomic physics is a continual striving to gain ever greater control over single quantum objects, starting with their internal degrees of freedom and now extending to their external degrees of freedom. Having learned to exert nearly complete control over single atoms, what are the new frontiers? One direction is to now exert similar levels of control over the interactions and correlations between atoms, with examples including quantum computing with trapped ions and quantum many-body simulations in degenerate atomic gases. Our lab has been asking the question: is it also possible to exploit atom-atom correlations and entanglement to advance the field of precision measurement beyond the single-atom paradigm that dominates the field? Using laser-cooled rubidium and strontium atoms inside of high finesse optical cavities, we have explored this question along two fronts: surpassing the standard quantum limit on quantum phase estimation by a factor of 60 and overcoming thermal limits on laser frequency stability. If time permits, I will also discuss the emergence of cavity-mediated spin-exchange interactions between the atoms, and the observation of a dynamical phase transition. By understanding what is possible to do with many atoms that we cannot do with just one, we hope to advance a range of technologies and science including realizing robust millihertz linewidth optical lasers, realizing advanced optical lattice clocks, and enhancing searches for new physics.
Professor James K. Thompson earned his undergraduate degree in Physics from Florida State University and his Ph.D. in Physics from the Massachusetts Institute of Technology. His doctoral work with David E. Pritchard focused on comparing the masses of two trapped ions with precision better than ten parts in a trillion for testing Einstein's mass-energy relationship E=mc2. As part of this work, James and his colleague Simon Rainville also discovered a novel method for making non-demolition measurements of the quantum state of single molecules. James was awarded the APS DAMOP thesis prize for this work. James moved to the MIT laboratory of Vladan Vuletic at the MIT/Harvard Center for Ultracold Atoms for his postdoctoral work, where he developed atomic quantum memories and entangled photon sources using laser-cooled atoms. Since moving to JILA and the Department of Physics at the University of Colorado, James's work has focused on studying how to exploit collective and quantum effects to advance precision metrology with cold atoms, and includes the demonstration of entangled spin-squeezed states and studies of superradiant lasers. He was awarded the Department of Commerce Bronze Medal for his work on superradiant lasers in 2013.
More details on James' research can be found here.