Optimal access to continuous-variable quantum information – Gandalf

Project GANDALF is set in the context of Quantum Information exploiting multipartite entanglement in observables with a continuous spectrum (also known as continuous variable regime, CV). Its main scope is to provide new experimental and conceptual tools to fully characterize multipartite states of light and apply them to distributed quantum sensing and quantum communication protocols. This goal opens to mid- and long-term applications, whose high societal and economic impact matches strategic objectives of information science and technology. In particular, CV frequency entanglement has been identified as an extremely rich and potentially disruptive quantum resource with applications in virtually all quantum technology fields: recent works have progressively shifted toward implementation in integrated optics and it is a strategic resource to invest on to push forwards practical uses of multimode quantum light. Project GANDALF starts from entanglement among frequency modes and addresses their optimal detection, with the scope of providing useful new conceptual and practical tools compatible with integrated resources. In CV quantum information, detection is more than a quantum diagnosis tool, but it is essential, for example, to implement the passage to different computational bases and in heralded state preparation. Based on previous works from the consortium, project Gandalf takes its moves from the observation that in many situations, standard CV detection based on homodyne detector leave part of the quantum information unmeasured and aims at demonstrating in experiments the advantage coming from a new general class of detectors that we indicated as interferometers with memory effect (IME).
The project originally develops in the context of quantum photonics sources integrated on Si-based platforms but goes beyond it. It will experimentally demonstrate strong, large-scale multipartite CV entanglement in regimes of intense and faint light, in Si-based integrated and bulk optics respectively. The French and U.S. experimental teams (INPHYNI and UVA) will collaborate to one another’s experiments, as they have in the past. The theory team at PhLAM will guide modeling, verification, and validation of multipartite quantum information, enabling complete characterization of CV quantum correlation using the concept of IME.