Experimental Preparation of Optical Cat States Carrying Orbital Angular Momentum

Abstract

As an important quantum resource, optical cat state is successfully prepared and applied in quantum information science. It is shown that optical quantum states carrying orbital angular momentum (OAM) have wide applications in quantum communication and quantum precision measurement. Here, optical cat states carrying OAM are experimentally prepared with topological charges $\ell$= 0, +1, +2, +4 by changing the wavefront of the photon-subtracted squeezed vacuum state with a combination of quarter-wave plate and q-plate. To verify the prepared cat states, both Wigner functions and topological charges of OAM are measured. It is shown that the fidelities and amplitudes of optical cat states carrying OAM decrease slightly with the increase of topological charges of OAM, although the spatial size of the optical beam is increased. These results present a new kind of optical cat state carrying OAM, which has potential applications in quantum precision measurement.