Microscopy of Bosonic Fractional Quantum Hall States in Optical Lattices

Harvard University, Cambridge MA

Investigators

Abstract

Fractional quantum Hall states, discovered by Tsui, Stormer and Gossard in two-dimensional electron systems, represent new states of matter that contain a novel kind of order - topological order. Understanding the physical origin that gives rise to such a behavior will profoundly enhance our perspective on topological materials and is promising for future applications such as topological quantum computers. However, the microscopic physics and quantum properties such as entanglement cannot be probed directly in quantum Hall condensed matter materials. Therefore, this project will build a model system using ultracold atoms in optical lattices. The atoms behave fully quantum mechanically and can serve as a quantum simulator. A quantum gas microscope enables full microscopic control, and will enable this team to shed light on the microscopic origin of fractional quantum Hall physics, and to directly probe quantum entanglement, which is essential for the future use of topological materials in quantum information. This project will also train students in atomic physics and condensed matter physics, and will help prepare them to participate in the high-tech work force. Since its discovery as quantized Hall conductance at fractional Landau level filling, the quantum Hall effect has been subject to intense theoretical and experimental study. Yet the microscopic mechanisms giving rise to many associated phenomena are not well understood, for example the nature of the many-body ground state, excitation properties (in particular the depedence on defects) or the role of a lattice structure. Theoretical studies suggest the fractional quantum Hall (FQH) effect should exist both for bosonic and fermionic particle statistics and have shown that the complexity arises from the interplay of strong interactions among the particles and topological features. This project will realize a system exhibiting the FQH effect by creating a strong synthetic gauge field in a few-boson system on a two-dimensional optical lattice. With the manipulation and detection techniques of a quantum gas microscope with single site resolution, this team will be able to determine the many-body state of the system by analyzing the density distribution on the level of single atoms. Furthermore, this team will work towards characterizing the global entanglement associated with the topological order by measuring the entanglement entropy of the system with a Hong-Ou-Mandel-type interference experiment. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.