School of Physics Colloquium: Dr. Xibo Zhang, JILA/University of Colorado/Boulder

Since the 2001 Nobel Physics Prize was awarded for the creation of Bose-Einstein condensates, dilute atomic gases at ultralow temperatures have been a driving force behind the quantum simulation of manybody physics. However, studying highly correlated quantum states with small energy gaps can still pose severe challenges to contemporary experiments with even the coldest atomic samples. The power of cold-atom experiments will be greatly enhanced by precision measurements, allowing, for example, physics that is normally probed at nK temperatures to be studied at μK temperatures. This is precisely what we have achieved. Thanks to the development of ultrastable lasers with 1×10-16 instability, the JILA strontium (Sr) optical clock now realizes a powerful laboratory to study a many-body spin system with strongly interacting, open, and driven dynamics [1]. For the first time, s- and p-wave inter-atomic interactions in the clock are characterized to high precision, which enables a spectroscopic observation of SU(N § 10) symmetry in 87Sr gases at μK temperatures [2]. This study lays the groundwork for pushing the frontier of emergent many-body quantum physics beyond experimental limitations, as well as realizing exotic quantum states that have no counterparts in nature.

To go beyond current experimental capabilities, one will need to combine the power of precision measurements with state-of-the-art cold-atom techniques to cool, probe, and manipulate atomic quantum gases. High-spatial-resolution imaging is one such technique, which has been utilized in the observation of quantum criticality with two-dimensional Bose gases in optical lattices [3]. In this experiment, high-resolution imaging allows one not only to access the equation of state and dynamics of a quantum gas, but also to engineer arbitrary trapping potentials for studying novel quantum transport phenomena. Based on my experiences with both ultracold atoms and precision measurements, I will discuss my future research plans and explain how ultracold strontium atoms with optical flux lattices will provide a unique opportunity to explore some of the most interesting strongly correlated quantum systems.

[1] A quantum many-body spin system in an optical lattice clock.

M. J. Martin, M. Bishof, M. D. Swallows, X. Zhang, C. Benko, J. von-Stecher, A. V. Gorshkov, A. M.

Rey, and J. Ye, Science 341, 632 (2013).

[2] Spectroscopic observation of SU(N)-symmetric interactions in Sr orbital magnetism.

X. Zhang, M. Bishof, S. L. Bromley, C.V. Kraus, M. Safronova, P. Zoller, A. M. Rey, and J. Ye, Science