Squeezing of X waves with orbital angular momentum

TL;DR

This paper explores the generation and properties of quantum X-waves with orbital angular momentum, demonstrating their resilience to diffraction and turbulence, and their potential for advancing free-space quantum communication and sensing technologies.

Contribution

It introduces the concept of propagation-invariant quantum X-waves with angular momentum and analyzes how spontaneous down-conversion can generate these states for quantum protocols.

Findings

Spontaneous down-conversion can generate squeezed X-waves.

Orbital angular momentum influences the squeezing angle.

A specific axicon aperture maximizes squeezing.

Abstract

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. Here we study propagation invariant quantum X-waves with angular momentum; this 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. We show that spontaneous down-conversion generates squeezed X-waves useful for quantum protocols. Surprisingly the orbital angural momentum affects the squeezing angle, and we predict the existence of a characteristic axicon aperture for maximal squeezing. 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.