Physics Department Colloquia

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Events on Tuesday, April 30th, 2024

Nano-Photonic Emitters for the “Quantum Age”: where imperfections lead to opportunities
Time: 3:30 pm - 5:00 pm
Place: Discovery Building, DeLuca Forum
Speaker: Evelyn Hu, Harvard University

Although we usually assume that a "perfect" material is required to produce the best emitters for nano-optical devices, defect states in wide bandgap semiconductors are defining a new frontier for quantum information technologies, offering correlated spin-photon information. Numerous materials platforms have been explored, including single crystal diamond, SiC and Si: ultimately these defect qubits will need to satisfy quantum systems-level requirements for coherence, brightness, and equivalence of states.

This talk will introduce some building-block devices for the evaluation of candidate defect qubits, with a focus on Silicon Vacancies in 4H-SiC. Nanobeam photonic crystal cavities serve as both exquisitely sensitive optical amplifiers [1], as well as "nanoscopes" that allow us to better understand the local environment of the silicon vacancies, interactions with proximal defects and pathways to better processing and control of the defects [2].

Forming defects directly into cavities by "Laser Writing" allows more rapid feedback of optimal defect formation conditions [3]. Embedding G-center defects in Si, within PN diodes allows a dynamic assessment of processing conditions and fine-tuning of defect properties [4]. In aggregate, these techniques help to build the foundational understanding to take defect qubits to the “next steps” in implementing new quantum information technologies.

[1] Bracher, David O., Xingyu Zhang, and Evelyn L. Hu. "Selective Purcell enhancement of two closely linked zero-phonon transitions of a silicon carbide color center." Proceedings of the National Academy of Sciences 114.16 (2017): 4060-4065.
[2] Gadalla, Mena N., Andrew S. Greenspon, Rodrick Kuate Defo, Xingyu Zhang, and Evelyn L. Hu. "Enhanced cavity coupling to silicon vacancies in 4H silicon carbide using laser irradiation and thermal annealing." Proceedings of the National Academy of Sciences 118, no. 12 (2021): e2021768118.
[3] Day, Aaron M., Jonathan R. Dietz, Madison Sutula, Matthew Yeh, and Evelyn L. Hu. "Laser writing of spin defects in nanophotonic cavities." Nature Materials (2023): 1-7.
[4] Day, Aaron M., Madison Sutula, Jonathan R. Dietz, Alexander Raun, Denis D. Sukachev, Mihir K. Bhaskar, and Evelyn L. Hu. "Electrical Manipulation of Telecom Color Centers in Silicon." arXiv preprint arXiv:2311.08276 (2023).

This event starts at 3:30pm with refreshments, followed at 3:45pm by a short presentation by Chengyu Fang (Mikhail Kats group), titled “Scalable passive optical masks that enable one- and two-species atom-trap arrays”. The invited presentation starts at 4pm.

Host: Mikhail Kats
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