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 Hoi1*
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