Quantum X waves with orbital angular momentum

Multi-level quantum protocols may potentially supersede standard quantum optical polarization-encoded protocols in terms of amount of information transmission and security. However, for free space telecomunications, we do not have tools for limiting loss due to diffraction and perturbations, as for example turbulence in air.

In a recent manuscript in arXiv, Marco Ornigotti, Leone di Mauro Villari, Alexander Szeimeit, and Claudio Conti study propagation invariant quantum X-waves with angular momentum. The adopted representation expresses the electromagnetic field as a quantum gas of weakly interacting bosons. The resulting spatio-temporal quantized light pulses are not subject to diffraction and dispersion, and are intrinsically resilient to disturbances in propagation. Spontaneous down-conversion generates squeezed X-waves useful for quantum protocols. Surprisingly the orbital angural momentum affects the squeezing angle, and a characteristic axicon aperture for maximal squeezing exists.

There results may boost the applications in free space of quantum optical transmission and multi-level quantum protocols, and may also be relevant for novel kinds of interferometers, as satellite-based gravitational wave detectors.