Abstract
Circuit quantum electrodynamics (C-QED) is referred to a circuit architecture by using artificial atom coupled to a microwave resonator as a laboratory to explore various fundamental interactions between light and matter. Here we investigate the quantum optics effects of a superconducting artificial atom, named transmon, strongly coupled to coherent microwave via one-dimensional transmission line, without resorting a cavity to confine the microwave photons. In particular, we deliberately implement transmon at the end of transmission, an anti-node position of microwave field. We measure the reflection and phase properties of system with frequency detuning and power modulation, and extract the transition frequencies of the atom via reflection measurement. We find that transmon acts as a mirror for a weak resonant probe-field, but behaves as a saturated atom as strongly probed. When we apply a strong control tone associated with the first-second state excitation, we observe clear Autler- Townes splitting. Our results demonstrate a first step toward using transmon to explore more intriguing quantum-optic phenomena. More experimental results and analysis will be presented and discussed.