Two-Mode Squeezed Quantum Microcombs on a Chip

The quest for building a fault-tolerant, universal quantum computer hinges on developing large-scale quantum systems while maintaining high quantum coherence. To address the scalability challenges, photonics offers optical multiplexing through spectral, temporal, and spatial properties of light to generate thousands to millions of quantum modes. These quantum modes can be entangled into cluster states which are essential for measurement-based quantum computation. Recent advancements in semiconductor fabrication technology allow the quantum modes to be generated on photonic integrated circuits and significantly enhance the scalability, footprint, and efficiency of photonic quantum systems.

One key focus of this dissertation is to generate chip-scale quantum sources through optical microresonators. The optical Kerr parametric process is employed to create unconditional entanglements via two-mode squeezed states, while the discrete resonant modes of the microresonator provide unique scalability through frequency multiplexing of these quantum states. A squeezed quantum microcomb was demonstrated in a silica wedge resonator on a silicon chip for the first time. A high-resolution quantum mode spectroscopy technique was developed to characterize the frequency equidistance of the squeezed microcomb. Additionally, we generated two counter-propagating squeezed microcombs in a single microresonator, providing a viable approach for creating chip-scale continuous-variable cluster states. Furthermore, 70 quantum modes were demonstrated using CMOS-compatible silicon nitride photonic integrated circuits, which have the potential to be heterogeneously integrated with other integrated photonic components for applications in quantum computing, communications, and sensing.