Person:

Shams Ansari, Amirhassan

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.

Quantum communications technologies require a network of quantum processors connected with low loss and low noise communication channels capable of distributing entangled states. Superconducting microwave qubits operating in cryogenic environments have emerged as promising candidates for quantum processor nodes. However, scaling these systems is challenging because they require bulky microwave components with high thermal loads that can quickly overwhelm the cooling power of a dilution refrigerator. Telecommunication frequency optical signals, meanwhile, can be fabricated in significantly smaller form factors while avoiding challenges due to high signal loss, noise sensitivity, and thermal loads due to their high carrier frequency and propagation in silica optical fibers. Transduction of information via coherent links between optical and microwave frequencies is therefore critical to leverage the advantages of optics for superconducting microwave qubits, while also enabling superconducting processors to be linked with low-loss optical interconnects. Here, we demonstrate coherent optical control of a superconducting qubit. We achieve this by developing a microwave-optical quantum transducer that operates with up to 1.18% conversion efficiency with low added microwave noise, and demonstrate optically-driven Rabi oscillations in a superconducting qubit.