Quantum violation of local causality in urban network with hybrid photonic technologies

Abstract

Quantum networks play a crucial role for distributed quantum information processing, enabling the establishment of entanglement and quantum communication among distant nodes. Fundamentally, networks with independent sources allow for new forms of nonlocality, beyond the paradigmatic Bell's theorem. Here we implement the simplest of such networks -the bilocality scenario-in an urban network connecting different buildings with a fully scalable and hybrid approach. Two independent sources using different technologies, respectively a quantum dot and a nonlinear crystal, are used to share photonic entangled state among three nodes connected through a 270 m free-space channel and fiber links. By violating a suitable non-linear Bell inequality, we demonstrate the nonlocal behaviour of the correlations among the nodes of the network. Our results pave the way towards the realization of more complex networks and the implementation of quantum communication protocols in an urban environment, leveraging on the capabilities of hybrid photonic technologies.

Experimental genuine tripartite nonlocality in a quantum triangle network

“…In spite of significant theoretical progress, understanding the correlations that such quantum networks can give rise to (see for instance the recent review [55]), the experimental side of this effort [56][57][58][59][60][61][62][63][64] is far less unexplored, due to a number of practical difficulties. In the particular case of a photonic platform, the most prominent of these difficulties stems from the probabilistic nature of the photons' generation and the synchronization process that becomes exponentially more demanding as the number of entanglement sources increase.…”