ABSTRACT
In this talk, I will address advances on quantum optics with superconducting artificial atoms in one dimensional (1D) space. In the first sets of experiments, we embed a transmon in 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 embed a transmon at a distance from the end (mirror) of a transmission line. By tuning the wavelength of the atom, we effectively change the normalized distance between atom and mirror, allowing us to effectively move the atom from a node to an antinode of the vacuum fluctuations. We probe the strength of vacuum fluctuations by measuring spontaneous emission rate of the atom [2]. In the third 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 [3]. In the fourth sets of experiment, we demonstrate that coherent-state microwave photons, with an optimal temporal waveform, can be efficiently loaded onto a single superconducting artificial atom in a semi-infinite 1D transmission-line waveguide. Using a weak coherent state (average photon number N<<1) with an exponentially rising waveform, whose time constant matches the decoherence time of the artificial atom, we demonstrate a loading efficiency of above 94% from 1D semi-free space to the artificial atom [4].
References
[1] P. Y. Wen et al. Physical Review Letters 120, 063603 (2018)
[2] I.-C. Hoi et al. Nature Physics 11, 1045 (2015)
[3] P. Y. Wen et al. Physical Review Letters 123, 233602 (2019)
[4] W. J. Lin et al. arXiv:2012.15084 (2021)
BIOGRAPHY
Dr. Io-Chun Hoi is an associate professor in the Department of Physics, National Tsing Hua University, Taiwan. He was an assistant professor at the same institute. He received B.S. and Ph.D. in Electro-Physics Department at National Chiao Tung University, Taiwan and Department of Microtechnology and Nanoscience, Chalmers University of Technology, Sweden, respectively. He did his postdoctoral research at University of California, Santa Barbara, U.S.A. He is the author or co-author of >20 publications, including 3 first-authored Physical Review Letters, 1 first-authored Nature Physics and 2 corresponding-authored Physical Review Letters. His research interest is experimental quantum optics and quantum computing with superconducting circuits.
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