We present a number of approaches, currently in experimental development in our research groups, toward the general problem of macroscopic quantum mechanics, i.e., manifestations of quantum noise and quantum fluctations with macroscopic (engineered and microfabricated by man) mechanical systems. Discussed experiments include a pendulum, a torsion pendulum, a ng-scale phononic-crystal silicon nitride membrane, a [Formula: see text] g-scale quartz resonator, and mg-scale mirrors for optical levitation. We also discuss relevant applications to quantum thermometry with optomechanical systems and the use of squeezed light to probe displacements beyond conventional quantum limits.
