Taming quantum noise: squeezed light in quantum sensing and communication

Light has long been a central platform for exploring quantum phenomena and for developing new technologies. Yet light is never completely ‘quiet’. Even under carefully controlled conditions, quantum fluctuations set fundamental limits on how precisely physical quantities can be measured and how efficiently information can be transmitted. At the same time, quantum physics offers tools to overcome some of these limits. One such tool is squeezed light, a specially engineered quantum state in which noise is reduced in one property of light at the expense of increased noise in its conjugate property.

In this lecture, I will introduce the key concepts behind continuous variable quantum optics and discuss the generation of squeezed light in nonlinear waveguides. To move squeezed light from specialised laboratory experiments to practical applications, however, these sources must be compact, stable and scalable. Waveguide platforms offer such a route and open the possibility of increasingly integrated quantum photonic technologies. I will then discuss how squeezed light can be used as a resource for quantum enhanced sensing and communication, with examples from precision interferometry and gravitational wave detection, biosensing and quantum key distribution. The lecture will show how controlling quantum noise in waveguide based systems can transform it from a fundamental limitation into a resource for future quantum technologies.