Topic: Optical Nonlinear Devices for Quantum Information Processing
Speaker: Professor Chen Xianfeng
Moderator: Professor Li Baojun
Date: April 19, 2019
Time: 15:00~16:00
Venue: Lecture Hall, Institute of Nanophotonics, Jinan University (Room 102, Heng Building, Panyu Campus)

Introduction to Speaker: Chen Xianfeng is an distinguished Professor of Shanghai Jiao Tong University, winner of National Science Fund for Outstanding Young Scholars , leading talent of National special support program for high-level personnel recruitment held by the organization department of the central committee of the CPC and the leading talent of Innovation Leadership Program in Science and Technologies for Young and Middle-aged Scientists. As the Excellent Academic Leader in Shanghai province, the winner of Education Ministry's New Century Excellent Talents Supporting Plan, he also awarded the title of “Shuguang” Scholar in Shanghai who enjoys special government allowances. He is the deputy director of the Basic Optics Committee of the China Optical Society, the Associate Editor-in-Chief of Chinese Optics Letters and the Associate Editor of Photonics Research. He is the editorial board member of Nonlinear Optical Physics and Material, and the standing editorial board member of Acta Optica Sinica. In the past decades, his research has been carried out in the fields of nonlinear optics, nanophotonics, photonic devices, laser physics and technology, and optoelectronic devices. He has published more than 200 papers in internationally important SCI journals such as Nature Photonics, Physical Review Letters, and Optics Letters. In 2010, he won the AAPS, C. N. Yang Award for his contribution in quasi-phase matching nonlinear optics and the interaction of light and nanostructured materials. He is currently the director of the Institute of Optical Science and Technology at Shanghai Jiao Tong University.

Abstract：
Single-photon frequency conversion for quantum interface plays an important role in quantum communications and networks, which is crucial for the realization of quantum memory,faithful entanglement swapping and quantum teleportation. In this talk, I will present our recent experiments about single-photon frequency conversion based on quadratic nonlinear processes. Firstly, we demonstrated spectrum compression of broadband single photons at the telecom wavelength to the near-visible window. A positively chirped single-photon-level laser pulse and a negatively chirped classical one are converted to a narrowband single-photon pulse, with a spectrum compression factor of 58, through sum-frequency generation (SFG), marking a critical step towards coherent photonic interface. Secondly, we demonstrated the nonlinear interaction between two chirped broadband single-photon-level coherent states. A high SFG efficiency of 1.06 × 10−7 is realized, which may be utilized to achieve heralding entanglement at a distance. Finally, we theoretically introduced and experimentally demonstrated single-photon frequency conversion in the telecom band, enabling switching of single photons between dense wavelength-division multiplexing channels. Using cascaded quasi-phase matched sum/difference frequency generation, the signal photon of a photon pair from spontaneous down-conversion is precisely shifted to identically match its counterpart, i.e. idler photon, in frequency to manifest a clear non-classical dip in the Hong-Ou-Mandel interference. Moreover, quantum entanglement between the photon pair is maintained after the frequency conversion. Our researches have realized three significant quantum interfaces via single-photon frequency conversion, which hold great promise for the development of quantum communications and networks.