Abstract:

Decoherence and the non-commuting nature of quantum variables are among the main challenges on the way to complete control of macroscopic systems. In this talk I will present two examples of generation of interesting quantum states of macroscopic systems. In the first experiment a Fock state of the collective spin of an atomic ensemble is created and then retrieved as a single photon on-demand. In the second experiment a measurement of motion of a mechanical oscillator with the precision exceeding the standard quantum limit is demonstrated. The origin of that limit is due to the random back action imposed on the momentum of an object when its position is measured. This randomness translates with time into position uncertainty, thus leading to the well known uncertainty on the measurement of motion, forces and fields. We have demonstrated that if the motion is measured in a special reference frame with an effective negative mass, there is practically no limit on the precision of the measurement. Applications of those ideas to force sensing including gravitational wave detection will be discussed.

Nature Physics 17, 228–233 (2021)

Nature Comm. 12, 3699 (2021)

Phys. Rev. Lett. 121, 031101 (2018).

Nature, 547, 191 (2017).