Demonstrating amplification inside the Mollow triplet
One of the most basic setups imaginable in quantum optics is a single two-level atom coupled to an electromagnetic environment. In 1969, Mollow famously predicted that if such an atom is strongly driven by light on its transition frequency, the resonance fluorescence will have peaks at three frequencies: the transition frequency of the atom and that frequency shifted up/down by the strength of the drive. A few years later, Mollow also studied theoretically what happens if a weak probe signal is added to this situation. Somewhat surprisingly, he found that the weak probe will be amplified if its frequency falls in-between the peaks of the Mollow triplet. In our article, we demonstrate such amplification much more clearly than ever before, using a superconducting qubit as the two-level atom to amplify a weak probe by 7%. In the figure, the three black lines in (b) are the Mollow triplet; the purple region is where our weak probe was amplified. (a) and (c) are data; (b) and (d) are theory plots without any free parameters.
Reflective amplification without population inversion from a strongly driven superconducting qubit
Ping Yi Wen, Anton Frisk Kockum, Hou Ian, Jeng-Chung Chen, Franco Nori, and Io-Chun Hoi
arXiv:1707.06400
