Special Seminar – Quanwei Li (University of California, Berkeley)

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1315 Seminar Hall
@ 3:30 pm

Title: Harnessing quantum light-matter interactions for quantum light spectroscopies and quantum information

Abstract: Quantum principles govern our world at the most fundamental level. They manifest themselves in non-classical phenomena such as single-quantum energy and non-local quantum entanglement. Harnessing these quantum principles promises revolutionary opportunities in not only quantum information but also new paradigms and physical tools for chemistry, biology, energy and materials, to gain insights in a new quantum domain that are not accessible by existing tools. Quantum light spectroscopies are such an emerging class of tools that explicitly exploit the quantum nature of light to unravel quantum effects in the properties and dynamics of complex material and/or biological systems. 

In this seminar, I will talk about my current and past research on harnessing quantum light-matter interactions for quantum light spectroscopies and quantum information, with the underlying key concepts in quantum optics introduced along the way. In the first part, we developed a photon-counting quantum light spectroscopy that probes natural photosynthetic light harvesting with a single photon at a time. We experimentally demonstrated that photosynthesis begins and proceeds with a single quantum of energy, going beyond the semi-classical picture of spectroscopy. Here, a complex biological system is prepared and studied with a single excitation, without perturbation by other photons or average over many simultaneous excitations. We also directly compared single photons and thermal light for photosynthetic light harvesting, towards clarifying the difference between photosynthesis in vivo and in laboratory. In the second part, we proposed and developed a unique non-unitary metasurface (i.e., artificial two-dimensional materials with subwavelength nanostructures), and we experimentally showed continuous tuning of the effective quantum interactions between single photons, through quantum two-photon interference, from boson-like to fermion-like. The results open a door to both innovative entangling gates for optical quantum information processing and fundamental quantum light–matter interactions that can be harnessed for new quantum light spectroscopies. I will conclude with a brief outlook for future directions.

Bio: Dr. Quanwei Li is currently a Postdoc at UC Berkeley Department of Chemistry working with Prof. Graham R. Fleming and Prof. Birgitta Whaley. Dr. Li’s postdoc research is focused on experimental development of new quantum light spectroscopies to study light absorption and energy transfer in natural photosynthesis for solar energy conversion and quantum effects in biology (Nature 2023, etc.). Dr. Li received his Ph.D. in Applied Science and Technology from UC Berkeley in Dec. 2019 under the supervision of Prof. Xiang Zhang. Dr. Li’s Ph.D. research was focused on experimental quantum light-matter interactions in a wide range of nanoscale systems including two-dimensional metasurface and Van der Waals materials for optical quantum information science and technologies (Nature Photonics 2021, etc.). Dr. Li received his B.S. in Physics with honor from Nanjing University in Jun. 2013.

Host: Prof. Marty Zanni