Dottorato in FISICA

Titolo della tesi: Quantum networks on a hybrid photonic platform

The goal of realizing large and interconnected quantum networks has gained a growing interest over the last decades. Indeed, they have the potential to disclose intrinsically secure and efficient quantum communication schemes and distributed quantum computing, connecting users with minimal quantum resources to powerful remote quantum processors and allowing them to run computational tasks that would be unfeasible with classical hardware. In this context, three fundamental challenges arise. First, it is pivotal to equip users with certification protocols for quantum devices, possibly relying on minimal assumptions about their inner working details, i.e. in a device-independent way. Second, users must be able to remotely access quantum servers while keeping hidden all data involved in their computations, through delegated blind quantum computing protocols. Finally, the realization of scalable quantum networks will be enabled by reliable and efficient quantum hardware, mostly based on photonic systems as quantum channels. Hence, the interest in the investigation of hybrid photonic platforms as systems for transferring and elaborating quantum information. This Ph.D. thesis investigates both software and hardware building blocks for hybrid photonic quantum networks. From the software point of view, it explores quantum foundations to device-independently certify quantum networks. In this direction, I will present two results. In the first one, I contributed to the first experimental demonstration of quantum effects in a scenario where standard techniques based on Bell tests would fail. In the second one, I contributed to developing a machine learning-based tool for the certification of arbitrarily large and complex quantum networks. Then, I contributed to the proposal of a versatile and scalable multi-client blind quantum computing protocol and provided the first experimental demonstration of a two-client blind quantum computing protocol. Finally, from the hardware point of view, I explore hybrid photonic platforms based on cutting-edge quantum dot single photon sources. In this direction, I will present two results. In the first one, I contributed to designing a modular plug-in optical platform for the generation of entangled quantum states tailored to single-photon sources. In the second one, I contributed to the investigation of a resonantly driven quantum dot photon source to provide the first experimental quantum teleportation of a genuine vacuum--one-photon qubit. The reported results may open promising perspectives toward the development of a large and secure quantum internet.