Quantum State Engineering of Macroscopic Oscillators

Recent ideas and technological developments have made possible studies of macroscopic objects deep in the quantum regime. In the talk I will discuss the experiment where an entangled Einstein-Podolsky-Rosen (EPR) state has been generated between distant mechanical and atomic oscillators [1]. The concept of an oscillator with an effective negative mass crucial for those experiments will be presented. Such entanglement allows to measure disturbances in the position and the momentum of an oscillator simultaneously, the trait which may seem counterintuitive. Using this entangled state, the trajectory of motion of the oscillator in phase space can be traced with, in principle, unlimited accuracy. Progress towards application of those ideas to gravitational wave detectors [2] following the proposals [3], [4] will be reported.