Abstract: When applied to practical problems, the very laws of quantum mechanics can provide a unique resource to beat the limits imposed by classical physics: this is the case of quantum metrology and high-precision sensing. Here we review the main results obtained in the recent years at the Quantum Technology Lab of the Department of Physics Aldo Pontremoli of the University of Milan, also in collaboration with national and international institutions. In particular we focus on the application of continuous-variable optical quantum states and operations to improve different fields of research, ranging from interferometry to more fundamental problems, such as the testing of quantum gravity.