Giacomo Sorelli | LIP6 - Équipe QI

Detecting a target with quantum entanglement

Mon, 20 Dec 2021 00:00:00 +0000

In the last decade a lot of research activity focused on the use of quantum entanglement as a resource for remote target detection, i.e. on the design of a quantum radar. The literature on this subject uses tools of quantum optics and quantum information theory, and therefore often results obscure to radar scientists. This review has been written with purpose of removing this obscurity. As such, it contains a review of the main advances in the quantum radar literature together accompanied by a thorough introduction of the quantum optics background necessary for its understanding.

Full characterization of the transmission properties of a multi-plane light converter

Fri, 01 Jan 2021 00:00:00 +0000

Multi-plane light conversion allows to perform arbitrary transformations on a finite set of spatial modes with no theoretical restriction to the quality of the transformation. Even though the number of shaped modes is in general small, the number of modes transmitted by a multi-plane light converter (MPLC) is extremely large. In this work, we aim to characterize the transmission properties of a multi-plane light converter inside and, for the first time, outside the design-modes subspace. By numerically reconstructing the transmission matrix of such systems, we individuate new ways to evaluate their efficiency in performing the design transformation. Moreover, we develop an analytical random matrix model that suggests that in the regime of a large number of shaped modes an MPLC behaves like a random scattering medium with limited number of controlled channels.

Photonic orbital angular momentum in turbulence: vortex splitting and adaptive optics

Mon, 21 Sep 2020 00:00:00 +0000

Recent works revealed that transmission of light beams carrying orbital-angular-momentum (OAM) through turbulence causes the optical vortex defining these beams to split into multiple vortices with unit topological charge. Here, we consider the numerical propagation of orbital-angular-momentum (OAM) modes through a horizontal atmospheric channel. By analysing the beam’s phase front after transmission through turbulence, we confirm the occurence of vortex splitting, but we also witness the emergence of vortex-antivortex pairs. Moreover, by performing performing a decomposition of the transmitted wave into OAM modes, we show that while adaptive optics cannot cancel vortex splitting, it still is pretty efficient in diminishing the turbulence-induced crosstalk between different OAM modes.

Entanglement of truncated quantum states

Wed, 01 Jan 2020 00:00:00 +0000

We investigate the impact of Hilbert-space truncation upon the entanglement of an initially maximally entangled m × m bipartite quantum state, after propagation under an entanglement-preserving n × n (n ≥ m) unitary. Truncation-physically enforced, e.g., by a detector’s finite cross section-projects the state onto an s × s-dimensional subspace (3 ≤ s ≤ n). For a random local unitary evolution, we obtain a simple analytical formula that expresses the truncation-induced entanglement loss as a function of n, m and s.