Light carries energy and both, linear and angular momentum. The total angular momentum can contain a spin contribution associated with polarisation, and an orbital contribution associated with the spatial profile of the light intensity and phase. The angular momentum of light can be used to generate quantum entangled photon states. The spin contribution is described by a two-dimensional state, thus can be employed to generate qubits, whereas the orbital contribution can generate higher dimensional quantum entangled states, or qunits, with an arbitrarily large number of entanglement dimensions. We have experimentally demonstrated that photons created by the spontaneous parametric down-conversion can be found to be entangled with respect to the orbital angular momentum. It was shown that orbital angular momentum entangled photons provide a manageable source for creation and manipulation of entanglement in higher dimensions. Using these techniques the non local feature of the higher dimensional entanglement was shown by violating a generalised type of the CHSH Bell's inequality. Our recent experiments include a scheme for concentration of higher dimensional entanglement and the demonstration of a quantum coin tossing protocol, which is the first quantum communication protocol using qutrits.

Contact: Luis A. Orozco.