Manipulate group delay via decoherence of a single artificial atom

Yu-Ting Cheng¹, Kai-Min Hsieh^1*, Bang-Yao Wu¹, Zheng-Qi Niu^2,3, Fahad Aziz⁴, Yu-Huan Huang⁴, Ping-Yi Wen⁵, Kuan-Ting Lin⁶, Yen-Hsiang Lin^4,7, Jeng-Chung Chen^4,7, Anton Frisk Kockum⁸, Guin-Dar Lin^6,9, Zhi-Rong Lin², Yong Lu^10,11,12, Io-Chun Hoi¹

¹Department of Physics, City University of Hong Kong, Kowloon, Hong Kong, China
²State Key Laboratory of Materials for Integrated Circuits, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, China
³ShanghaiTech University, Shanghai, China
⁴Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
⁵Department of Physics, National Chung Cheng University, Chiayi, Taiwan
⁶CQSE, Department of Physics, National Taiwan University, Taipei, Taiwan
⁷Center for Quantum Technology, National Tsing Hua University, Hsinchu, Taiwan
⁸Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Gothenburg, Sweden
⁹Physics Division, National Center for Theoretical Sciences, Taipei, Taiwan
¹⁰Guangzhou Institute of technology, Xidian University, Xi’an, China
¹¹Advanced Interdisciplinary Research Center, Xidian University, Xi’an, China
¹²Faculty of Integrated Circuit, Xidian University, Xi’an, China

* Presenter:Kai-Min Hsieh, email:tomnet1004@gmail.com

The ability to slow down light at the single-photon level has significant implications for quantum information processing and other quantum technologies. In this work, we demonstrate two methods for dynamically controlling the velocities of microwave light in waveguide quantum electrodynamics (waveguide QED) using a single artificial atom. These methods rely on the balance between the radiative and non-radiative decay rates of a superconducting artificial atom placed in front of a mirror. The first method involves tuning the atom's radiative decay using interference effects created by the mirror. The second method utilizes the Autler–Townes effect to control the atom's non-radiative decay by pumping it. When half of the radiative decay rate exceeds the non-radiative decay rate, a positive group delay is observed. Conversely, when the non-radiative decay rate dominates, a negative group delay occurs. Our findings enhance the signal-processing capabilities in waveguide QED.

Keywords: Negative group delay, Positive group delay, Superconducting artificial atom, Waveguide QED