Electronically programmable photonic molecule

Physical systems with discrete energy levels are ubiquitous in nature and form fundamental building blocks of quantum technology. Artificial atom-like and molecule-like systems were previously demonstrated to regulate light for coherent and dynamic control of the frequency, amplitude and the phase of photons. In a recent study, Mian Zhang and colleagues engineered a photonic molecule with two distinct energy levels, using coupled lithium niobate micro-ring resonators that could be controlled via external microwave excitation. The frequency and phase of light could be precisely operated by programmed microwave signals using canonical two-level systems to include Autler-Townes splitting, Stark shift, Rabi oscillation and Ramsey interference phenomena in the study. Through such coherent control, the scientists showed on-demand optical storage and retrieval by reconfiguring the photonic molecule into a bright-dark mode pair. The dynamic control of light in a programmable and scalable electro-optic system will open doors for applications in microwave-signal processing, quantum photonic gates in the frequency domain and to explore concepts in optical computing as well as in topological physics.