Abstract: In this talk, I will address recent advances in 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. 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. 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. 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

Bio：

Research area

Experimental quantum optics and quantum information with superconducting circuits.

Appointment

Associate professor, Department of Physics, 2021-present

City University of Hong Kong, Hong Kong, China

Education

Ph.D., Department of Microtechnology and Nanoscience, 2008-2013

Chalmers University of Technology, Sweden.

Supervisors: Prof. Per Delsing and Prof. Christopher Wilson

Dissertation: “Quantum Optics with Propagating Microwaves

in Superconducting Circuits”

M.Sc., Nanoscale Science and Technology Programme, 2006-2008

Chalmers University of Technology, Sweden.

Exchange student at Chalmers University of Technology, Sweden. 2006-2007

B.Sc., ElectroPhysics, National Chiao Tung University, Taiwan 2003-2007