Dissipation is generally a bad thing for quantum systems, robbing them of their special quantum features of coherence, superposition, and entanglement, and driving them to classical behavior. This project will endeavor to use dissipation in quantum systems for positive benefit. The research will develop techniques to use dissipation to remove unwanted energy, entropy, and randomness from a quantum system while preserving the wanted quantum information. A matter wave analogy to the field of quantum optics will be pursued, so that the important features that arise from interaction of matter with light can be replicated and perhaps expanded in a solely matter-based system.
This research resides at the intersection of atomic physics, quantum information science, and condensed matter physics. Developing ways to engineer dissipation and understand and control open quantum systems will be relevant to virtually any new technological applications built on quantum mechanics, from a fully realized quantum computer to much more modest applications such as sensors based on coherent quantum mechanical processes. Graduate and undergraduate students will be trained in state-of-the-art science in an environment that exposes them to a wide variety of physics and research in both an academic and national lab setting.
We have created a versatile experimental system that can simultaneously confine two different elements, rubidium and ytterbium, at temperatures just above absolute zero. This system will allow the study of controlled dissipation in quantum systems. Usually dissipation is the enemy of "quantumness", as it can destroy quantum information, but it can also be useful and necessary to control. Any realistic quantum information device is an open system (it has to be connected to the outside world for control), and dissipation may be used to remove unwanted entropy from the system. The system we have developed confines one species in an optical lattice, immersed in an ultracold bath of the other species. The system is analogous to quantum optics, where atoms are coupled to the photon vacuum, except that here the atoms are coupled to the "vacuum" of the atomic bath of the other species. Using matter waves will allow a deeper understanding and possible control in the world of open quantum systems. Our experimental apparatus has successfully produced large Bose Einstein condensates of rubidium and has laser cooled and trapped ytterbium. The new apparatus has already enabled spin off applications with impact on advanced atomic clocks. One of the critical aspects of this work is to form an optical lattice to trap ytterbium that is invisible to rubidium atoms. This invisibility is necessary for future experiments on engineered dissipation, but accurate measurements of the vanishing lattice also allow for the determination of essential atomic properties of the rubidium atom. We have performed measurements of the size of the optical forces in rubidium atoms near where the atom-light interaction vanishes by developing a new technique based on atomic diffraction to measure very small optical forces. With the new technique, we accurately measured the size of the matrix elements of optical transitions in rubidium. These previously unknown properties of rubidium were one of the leading uncertainties in rubidium based atomic clocks, and the new measurement have an immediate impact on the accuracy of advanced frequency standards The major progress from this award has been the construction of a versatile and unique apparatus to allow the exploration of engineering and modification of quantum dissipation. This provides valuable educational experience in a wide variety of advanced technologies for the undergraduate and graduate students working on the project, helping to provide an advanced workforce for the 21st century. As quantum information science continues to develop toward physical devices, understanding and controlling quantum dissipation will be a critical component.
