Prof. Xiong-Jun Liu and collaborators publish a paper in Nature Physics reporting Quantum Simulation of 3D Topological Matter with Ultracold Atoms

Physicists from Peking University (PKU) and the Hong Kong University of Science and Technology (HKUST) have proposed and successfully realized for the first time a 3D simulation of topological matter consisting of ultracold atoms. Previous attempts at topological matter simulations were limited to one and two dimensions, due to challenges on how to characterize 3D band topology in atomic systems. This breakthrough paves an opening to further examining new topological matter that cannot be well realized in solids. Such never-before-done engineering artificial material with ultracold atoms may allow physicist to model unusual phases of matter.

This work was led by Prof. Xiong-Jun Liu, a Professor from the School of Physics at PKU, and Prof. Gyu-Boong Jo, an Associate Professor from the Department of Physics at HKUST. They created an artificial crystal lattice structure, which was previously proposed by the PKU group, to model ultracold atoms prepared at 30 billionths of a degree above absolute zero.  This new synthetic quantum matter is a 3D spin-orbit coupled nodal-line topological semimetal, which exhibits an emergent magnetic group symmetry. With such emergent symmetry the researchers proved in theory that the 3D band topology can be resolved by only imaging 2D spin patterns on the symmetric planes, and further successfully observed the 3D topological semimetal in experiment. The detection technique proposed and used here can be generally applied to exploring all 3D topological states of similar symmetries when those become available.

The research was recently published online in Nature Physics [Nat. Phys. 15, 911-916 (2019); DOI:10.1038/s41567-019-0564-y].

Complex topological matter has become the focus of both academic and industrial research because it is seen as a way to pave the way to making information and computation devices more noise free and robust. For example, today’s physical quantum computers are still noisy, and quantum error correction is a growing field of research. The goal of fault tolerant quantum computing has driven investment into complex topological matter. Exploring the topological quantum states with quantum simulators like ultracold atoms can enable the precise studies of every aspect of the exotic states, and broaden the understanding of the fundamental phases of nature.

This work signifies a breakthrough progress for quantum simulation with ultracold atoms. In particular, the technique reported in the work enables the experimental investigation and observation of nontrivial phases of all physical dimensions, including various insulating, semimetal, and superfluid phases with nontrivial topology in ultracold atoms. As result, this development expands the ability to explore complex topological matter in 3D, and will open up a promising avenue for quantum simulation with ultracold atoms.

This work is a further research of the previous work published by the collaborating team in Science Advances 4, eaao4748 (2018). The work was supported by National Natural Science Foundation of China, National Key R\&D Program of China, and Strategic Priority Research Program of Chinese Academy of Science.