Person:

Zhang, Mian

Physical systems with discrete energy levels are ubiquitous in nature and are fundamental building blocks of quantum technology. Realizing controllable artificial atom- and molecule-like systems for light would enable coherent and dynamic control of the frequency, amplitude and phase of photons. In this work, we demonstrate a ‘photonic molecule’ with two distinct energy levels using coupled lithium niobate microring resonators and control it by external microwave excitation. We show that the frequency and phase of light can be precisely controlled by programmed microwave signals, using concepts of canonical two-level systems including Autler–Townes splitting, Stark shift, Rabi oscillation and Ramsey interference. Through such coherent control, we show on-demand optical storage and retrieval by reconfiguring the photonic molecule into a bright–dark mode pair. These results of dynamic control of light in a programmable and scalable electro-optic system open doors to applications in microwave signal processing, quantum photonic gates in the frequency domain and exploring concepts in optical computing8 and topological physics.

Efficient frequency shifting and beam splitting is important for a wide range of applications, including atomic physics1,2, microwave photonics3–6, optical communication7,8, and photonic quantum computing9–14. However, realizing gigahertz-scale frequency shifts with high efficiency, low loss, and tunability, in particular using a miniature and scalable device, is challenging since it requires efficient and controllable nonlinear processes. Existing approaches based on acousto-optics6,15–17, all-optical wave mixing10,13,18–22, and electro-optics23–27 are either limited to low efficiencies or frequencies, or are bulky. Furthermore, most approaches are not bi-directional, which renders them unsuitable for frequency beam splitters. Here we demonstrate electro-optic frequency shifters that are controlled using only continuous and single-tone microwaves. This is accomplished by engineering the density of states of, and coupling between, optical modes in ultra-low loss waveguides and resonators in lithium niobate nanophotonics28. Our devices, consisting of two coupled-ring-resonators, provide frequency shifts as high as 28 GHz with an ~90% on-chip conversion efficiency. Importantly, the devices can be reconfigured as tunable frequency-domain beam splitters. Using the device, we also demonstrate a non-blocking and efficient swap of information between two frequency channels. Finally, we propose and demonstrate a scheme for cascaded frequency shifting that allows shifts of ~120 GHz using a ~30 GHz continuous and single-tone microwave signal. Our devices could become building-blocks for future high-speed and large-scale classical information processors7,29 as well as emerging frequency-domain photonic quantum computers9,11,14.