A dark horse approach to universal, fault tolerant quantum computing at utility scale has been to use light and, in particular, to use its continuous quantum optical fields rather than single-photon qubits. Two major promises of photonic quantum computing are: (i), its outstanding scalability potential, which far surpasses that of all other platforms, and (ii), the prospect of operating at or near room temperature (as well as atmospheric pressure). Over the years, efforts have been made to move from the pioneering quantum optics experiments in free-space optics, which established QC feasibility, to integrated photonics on chip. I will review the basic concepts, progress, and prospects.

Quantum fluids and solids (QFS) exhibit remarkable macroscopic quantum phenomena and provide exceptionally clean environments for exploring fundamental physics and developing emerging quantum technologies. Superfluid helium-4 (He II), for example, supports frictionless superflow and quantized vortices, while cryogenic surfaces such as liquid helium and solid neon can naturally trap electrons in vacuum with minimal environmental disturbance. In this colloquium, I will discuss our efforts to explore and harness these unusual properties of cryogenic quantum matter. I will begin by introducing He II as a model quantum fluid and describing advanced flow-visualization techniques that allow us to directly probe quantized vortex dynamics, quantum turbulence, and related nonequilibrium phenomena. I will highlight our recent studies of vortex reconnections, quantum dissipation associated with vortex rings, and coherent vortex structures. I will then turn to emerging opportunities for using quantum fluids as platforms for quantum sensing, including our recent work with magnetically levitated He II droplets. Finally, I will discuss our efforts to develop qubits based on single electrons trapped on solid neon surfaces. Recent electron-on-neon experiments have demonstrated excellent coherence, but scaling the platform to larger and more controllable qubit arrays remains a major challenge. I will describe a new architecture based on magnetically levitated solid-neon microparticles that may offer a pathway toward scalable electron-qubit systems. Together, these studies illustrate how quantum fluids and solids can bridge fundamental discoveries in macroscopic quantum physics with emerging opportunities in quantum science and technology.