Integrated Lithium Niobate Photonics for Quantum Technologies

We are entering an age where we can engineer and build machines that are enhanced by the principles of quantum mechanics. These new machines will dramatically change the way we compute, sense the world around us, and communicate. Quantum technologies of all kinds face two major challenges: individual device performance and scalability. Device performance improvements have been dramatic in recent years with superconducting qubit coherence times growing by orders of magnitude in the past decade, for example. However, individual device performance alone will not usher in a new era of quantum technologies. Systems of scale require high performing devices that can be combined in new and expansive ways. Large-scale quantum systems promise to revolutionize drug discovery, materials science research, secure communications, and the simulation of quantum physics itself. These applications require systems with orders of magnitude more entanglement than is currently possible. Scale has two parts: the number of devices integrated locally into a system and the number of systems interacting over distance. Moving to chip-scale integration can benefit both scalings since many devices can be integrated on the surface of a single chip, and nanoscale integrated systems promise performance benefits for efficient transduction to connect distant systems.

The first part of this dissertation describes my work towards building efficient transducers to coherently connect quantum machines based on superconducting microwave qubits over large distances. This effort used thin-film lithium niobate nanophotonic devices integrated with superconducting circuits on the same chip with the goal of providing a transparent link between quantum computers over standard optical fiber infrastructure. The second part of this dissertation describes a comprehensive demonstration of resonant second-order nonlinear integrated photonic systems based on thin-film lithium niobate. We built an on-chip optical parametric oscillator that improved upon the state of the art by three orders of magnitude in threshold power and sets the standard for device performance in X-cut lithium niobate. The demonstrated chip-scale nonlinear circuits can now be expanded to scalable quantum computing architectures based on entangled optical modes and enhanced quantum sensing with squeezed light.