Quantum optics with superconducting artificial atoms

P. Y. Wen¹, K.-T. Lin², A. F. Kockum³, G.-D. Lin², J. C. Chen¹, P. Delsing³, F. Nori⁴, IoChun Hoi^1*

¹Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
²Department of Physics, National Taiwan University, Taipei, Taiwan
³Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg, Sweden
⁴Theoretical Quantum Physics Laboratory, RIKEN Cluster for Pioneering Research, Wako-shi, Japan

* Presenter:IoChun Hoi, email:hoiiochun@gmail.com

In this talk, I will address advances on quantum optics with superconducting artificial atoms. In the first sets of experiments, we embed a transmon at the end of a transmission line. When driving the qubit strongly on resonance such that a Mollow triplet appears, we observe a few percent amplitude gain for a weak probe at frequencies in-between the triplet. This amplification is not due to population inversion, but instead results from a four-photon process that converts energy from the strong drive to the weak probe [1]. In the second sets of experiment, we place two superconducting qubits in a transmission line terminated by a mirror, which suppresses decay. We measure a collective Lamb shift reaching 0.8% of the qubit transition frequency and exceeding the transition linewidth [2]. We also show that the qubits can interact via the transmission line even if one of them does not decay into it.


[1] P. Y. Wen et al. Physical Review Letters 120, 063603 (2018)
[2] P. Y. Wen et al. arXiv:1904.12473 (2019)

Keywords: transmon, Mollow triplet, four-photon process, collective Lamb shift