內容：

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.

人物介紹：

美國聯合量子研究所 (Joint Quantum Institute, University of Maryland and the National Institute of Standards and Technology) JQI Postdoc Fellow and Research Scientist。 杜克大學物理學博士碩士, 北京大學光學碩士, 中山大學物理學學士。多年來在實驗原子分子光物理領域有著活躍的學術研究，涉及冷原子物理，囚禁離子量子計算，原子光子量子網絡，空腔電子電動力學，超快光學等多個前沿領域。

   費米原子凝聚是繼冷原子實驗技術和玻色愛因斯坦凝在1997年和2001年分別獲得諾貝爾物理學獎之后冷原子物理領域又一里程碑。我在這一領域的貢獻包括首次從實驗上得到了強相互作用費米氣體的溫標并確定了費米凝聚的相變溫度，實施了第一個不依賴理論模型的熱力學測量從而在實驗上驗證了強相互作用量子體系中的普適熱力學預言，首次在強相互作用的量子流體中觀測到接近弦理論所預言的量子極限的流體性，以及在實驗中首次觀測到費米氣體的自旋分離。囚禁離子是目前最有希望實現量子計算和量子網絡的物理體系。我最近在這一領域的工作包括通過遠距離間兩個離子的糾纏實現第一個量子隨機數產生器，提出可拓展的原子光子量子網絡實驗方案，結合囚禁離子阱與空腔電子電動力學技術實施增強的量子界面，以及在半導體芯片離子阱上實施量子邏輯門。獲得的學術獎勵，包括獲得美國聯合量子研究所第一個實驗物理方向上的JQI Postdoc Fellowship, Fritz London 博士研究生獎，中國政府海外優秀自費留學生獎，王大珩光學獎學生獎。在重要期刊上發表過超過二十篇論文，其中多篇發表在Nature和Physics Review Letters，并以"費米氣體熱力學"和"原子光子量子網絡"為主題發表過兩個長篇綜述。

   目前的學術興趣包括兩個方面，一方面以超冷量子氣體為實驗工具探索在多體和少體量子物理領域具有普適性的問題，實現凝聚態與核物理領域一些基礎問題的冷原子量子模擬，并探索進行拓撲量子計算的可能性。另一方面以囚禁離子為工具，實現大規模的量子糾纏和量子邏輯，實現大空間尺度可拓展的原子光子量子網絡，為最終實現量子信息處理奠定物理的基礎。