Title：Bottom-up and Top-down in Atomic Physics: Ultracold Atom Quantum Simulator and T
Speaker： Le Luo
Time： 2011-04-07 15:00-2011-04-07 16:45
In Tsinghua-IIIS-CQI, we are targeting the cutting edge researches in quantum information based on atomic, molecular and optical physics. We are planning to implement several research projects that are able to win international reputation and train top postdoc and graduate students in several years. In Chinese words, that is a “Big Movement Fast Growing (da kan kuai shang)” strategy. At the technical level, we are extremely cautious to pick up our road map. In this talk, I will present two research directions that have substantial potentials. These two directions are complementary: One is to use laser cooled and trapped neutral atoms for a top-down study of quantum physics; the other is to use trapped ions for a bottom-up study. Specifically I will use ultracold Fermionic atoms and ion-photon network as examples.
Ultracold Fermi atoms provide a paradigm system to explore intriguing many-body physics in a wide range of exotic systems, including high-temperature superconductors, neutron stars, the quark-gluon plasma, and black holes in string theory. All those systems have universal thermodynamics and hydrodynamics governed by the nature of unitary strong interactions. In such sense, a table-top experiment with laser-cooled and trapped Fermionic atoms is an ideal ultracold quantum simulator for the condensed matter and nuclear physics. I will review my experimental work including all-optical method for producing degenerate and strongly interacting Fermi gases, probing the universal thermodynamics by implementing the first model-independent thermodynamic measurement, obtaining the thermometry of strongly interacting Fermi gases experimentally and thus determining the critical temperature of Fermi condensation, and the first study of the quantum viscosity behavior in the unitary regime. My focus is in search of a so-called perfect fluid that has exceedingly low shear viscosity and possible existed in strongly interacting systems. Unlike a superfluid, such perfect fluid is not in a single quantum state but a many-body quantum phenomenon which could connect to string theory. Our results from both thermodynamic and hydrodynamic measurements confirm that a strongly interacting Fermi gas enters into the perfect fluidity regime and is very close to the estimation data from the quark-gluon plasma.
Quantum networks based on trapped atomic ions and scattered photons provide a promising way to build a large scale quantum information processor. Such systems promise storing and processing information in a way that could eclipse the performance of conventional computers. Previous work has demonstrated generating entanglement and operating gates between two distant trapped ion qubits. Recently we also realize several quantum algorithms including the first quantum random number generator by using remote entangled ions. In particular, enhancing the collection of spontaneous emitted photons from trapped ions is likely to help scaling up atom–photon quantum networks in the next several years. By integrating a micro-fabricated ion trap with a cavity QED system in the intermediate coupling regime, we recently observe an enhancement of the spontaneous emission from a single trapped ytterbium ion into a cavity mode by a factor of hundreds comparing with the free-space emission. Such ion cavity systems provide a platform to realize a large scale atom-photon quantum network that could possibly close both locality and detection holes in a Bell test experiment. Furthermore, trapped charged particles inside an optical cavity open the door for the potential applications in other fields such as trapping mesoscopic material and biomolecule for optical study.
Le Luo currently is a research scientist and JQI postdoctoral fellow in Joint Quantum Institute, University of Maryland and the National Institute of Standards and Technology. He obtained Ph.D. and M.A in Physics at Duke University, and M.S. in Optics at Peking University, and B.S. Physics with honors at Sun Yat-sen University. In the past ten years, he is an active researcher in experimental atomic, molecular and optical physics, contributing to several cutting-edge fields including cold atom physics, trapped ion quantum information, atom-photon quantum network, cavity quantum electrodynamics, and ultrafast optics.