Continuous Variable Entanglement in Non-Zero Orbital Angular Momentum States

Abstract

Orbital angular momentum is a discrete degree of freedom that can access an infinite dimensional Hilbert space, thus enhancing the information capacity of a single optical beam. Continuous variables field quadratures allow achieving some quantum tasks in a more advantageous way with respect to the use of photon-number states. Here, we use a hybrid approach realizing bipartite continuous-variable Gaussian entangled state made up of two electromagnetic modes carrying orbital angular momentum. A q-plate is used for endowing a pair of entangled beams with such a degree of freedom. This quantum state is then completely characterized thanks to a novel design of a homodyne detector in which also the local oscillator is an orbital angular momentum-carrying beams so allowing the direct detection of vortex modes quadratures.

High-Rate Continuous-Variable Quantum Key Distribution with Orbital Angular Momentum Multiplexing

“…As a new additional degree of freedom, OAM is completely independent from wavelength, frequency, polarization, and so on [ 35 ]. Unlike other degrees of freedom, the OAM of light can construct an infinite-dimensional Hilbert space, where the quantum coding can be achieved on the orthonormal basis formed by the OAM states [ 34 , 36 ].…”