• Physicists classify and understand systems in terms of many properties; color, mass, length and microscopic symmetries are familiar examples. Another interesting feature is a system’s topology, or how its parts connect. As an example, a circular linked necklace can be deformed into an oval or a rectangle without changing the topology, since the links remain connected in the same way. But the necklace can only be made into the topologically distinct straight line if it is cut or its clasp is opened. In the 1980s physicists realized that some physical properties are entirely dictated by a system’s topology. 

    Our group investigates topological features in optical systems to explore new physics and develop optical devices with built-in protection. For more information, you can read the recent Quick Study in Physics Today.

  • When the interaction between particles in a physical system is weak, particles can be considered to act independently. In this situation, linear analysis such as band theory (coupled-mode theory) for electronic (photonic) systems is valid. However, when the interaction between particles is very strong, the quantum state of the system is no longer separable, and therefore, the system should be treated in its entirety. In our group, we explore quantum dynamics of strongly interacting photonic systems. In the context of quantum simulation, we investigate optical phenomena related to well-known effects in condensed matter physics such as quantum Hall physics and also lattice gauge theories. Moreover, we explore novel effects specific to optical systems, such as dissipative-driven phenomena.

     

    More generally, we investigate how a many-body system can be theoretically characterized, e.g., entanglement spectrum, and efficiently prepared and probed in an experimental setting. 

  • Controlling the interaction between quantum bits and electromagnetic fields is a fundamental challenge underlying quantum information science. Ideally, control allows storage, communication, and manipulation of the information at the level of single quanta. Unfortunately, no single degree of freedom satisfies all these criteria simultaneously. Instead, a hybrid approach may take advantage of each system’s most attractive properties. For example, optical photons provide a robust long-distance quantum bus, while microwave photons can be easily manipulated using superconducting qubits, and atoms can store quantum information for seconds or even minutes. In our group, we investigate various hybrid scenarios for applications in classical and quantum information processing and quantum simulation.   Moreover, we exploit these hybrid approaches to probe and manipulate many-body quantum states, such as optical manipulation of electronic topological states.