Nicolas Laurent-Puig

Quantum Key Distribution (QKD) enables Information-Theoretically Secure (ITS) key exchange, robust even against future quantum computing threats. However, a fundamental limitation of QKD is the requirement for an authenticated classical channel, which necessitates a pre-shared secret key. In this letter, we address this dependency by integrating a Hybrid Physical Unclonable Function (PUF) protocol. We demonstrate that this PUF-based method generates an ITS initial key under minimal explicit hardware assumptions. This approach establishes a fully ITS-authenticated QKD protocol that relies solely on hardware assumptions, effectively eliminating the need for manually pre-shared secrets. This represents a significant step toward practical realization of quantum network protocols using lightweight, readily available hardware assumptions, without weakening security guarantees.

Quantum sensors are powerful tools for measuring physical quantities with high sensitivity, enabling, for instance, the mapping of Earth’s gravitational field , detecting very small changes of magnetic fields, or the passage of time. The underlying principle is to use a quantum state as a probe that interacts with the physical quantity of interest, thereby encoding relevant information into the state. Although individual quantum sensors may exhibit remarkable sensitivity, the precision of a certain measurement can be significantly enhanced when multiple probes are entangled. Distributed quantum sensing extends this further and leverages entanglement among spatially separated sensors, allowing them to function as a single, coherent system. This approach enables measurements across extended spatial regions, while surpassing the precision achievable by independent sensors. However, a significant challenge in a network setting is ensuring that sensors deployed across different parties serve as the necessary resources for the correct functioning of the target sensing task. This challenge has motivated the combination of quantum cryptography with quantum sensing. In this context, Shettell et al. introduced the notion of privacy for sensor networks, ensuring that, beyond the metrological advantage of cooperative estimation of a global function, parties can also maintain the privacy of their local information and control what data is accessible to others. In this work, we adopt this protocol and focus on a multi-user quantum sensor network framework to analyze the privacy aspects of this parameter estimation task, leveraging a high-quality four-party GHZ state source.

Authentication of quantum resources is a critical tool in the development of quantum information processing protocols. In particular, the verification of quantum states is often used as a building block for communication tasks, determining whether the communicating parties can trust the resources at hand to exchange information or whether the protocol should be aborted. Self-testing methods have been used to tackle such verification tasks in a device-independent (DI) scenario. However, these approaches commonly consider the limit of large, identically and independently distributed (IID) samples, which weakens the DI claim and poses serious challenges to their experimental implementation. To address these issues, Gocanin et al. [1] developed a protocol to certify quantum states in the few-copies and non-IID regime. In this work, we adopt their protocol to experimentally demonstrate the device-independent verification of a four-photon GHZ state, produced with our compact and high-fidelity multipartite entangled photon source.

Quantum information protocols offer significant advantages in properties such as security, anonymity, and privacy for communication and computing tasks. An application where guaranteeing the highest possible security and privacy is critical for democratic societies is electronic voting. As computational power continues to evolve, classical voting schemes may become increasingly vulnerable to information leakage. In this work, we present the experimental demonstration of an information-theoretically secure and efficient electronic voting protocol that, crucially, does not rely on election authorities, leveraging the unique properties of quantum states. Our experiment is based on a high-performance source of Greenberger–Horne–Zeilinger (GHZ) states and realizes a proof-of-principle implementation of the protocol in two scenarios: a configuration with four voters and two candidates employing privacy enhancement techniques and an election scenario supporting up to eight voters and sixteen candidates. The latter is particularly well-suited for secure board-level elections within organizations or small-scale governmental contexts.