Środowiskowe Seminarium z Informacji i Technologii Kwantowych

Rapid advancements in photonic, atomic and solid-state quantum information experiments have seen a steady increase in the sophistication of quantum communication networks now and in the near future. This presents two significant theoretical challenges: the increasing complexity of modelling and analysis and the quest for new protocols that optimally exploit such multipartite networks. This talk will present several results on the performance advantages for multipartite entanglement in quantum cryptography. First, we prove the security of a variant of the GHZ-state based secret sharing protocol against general attacks, including participant attacks which break the security of the original GHZ scheme [1]. We then identify parameters for a performance advantage of multipartite protocols over any bipartite protocols for both secret sharing and conference key agreement over bottleneck (star) networks. Secondly, we will show how recent advances in the study of nonlocality over so-called broadcast network can be exploited to improve the robustness of device-independent random number generation (DI-RNG). We present a theoretical analysis and proof-of-principle experimental demonstration of DI-RNG in a tripartite broadcast network using initial bipartite states that are Bell local [2]


[1] Memmen, J., Eisert, J. & Walk, N. Advantage of multi-partite entanglement for quantum cryptography over long and short ranged networks. arXiv:2312.13376 (2023)
[2] Polino, E. et al. Experimental quantum randomness enhanced by a quantum network. arXiv:2412.16973 (2024).