2000 seminars


Room P5.18, Mathematics Building

Gláucia Murta

Gláucia Murta, Heinrich-Heine-Universität Düsseldorf
Secure Anonymous Conferencing in Quantum Networks

Users of quantum networks can securely communicate via so-called (quantum) conference key agreement, making their identities publicly known. In certain circumstances, however, communicating users demand anonymity. In this talk, I will introduce a security framework for anonymous conference key agreement with different levels of anonymity and present efficient and noise-tolerant protocols exploiting multipartite Greenberger–Horne–Zeilinger (GHZ) states.

We compare the performance of our protocols in noisy and lossy quantum networks with protocols that only use bipartite entanglement to achieve the same functionalities. Our simulations show that GHZ-based protocols can outperform protocols based on bipartite entanglement and that the advantage increases for protocols with stronger anonymity requirements. Our results strongly advocate the use of multipartite entanglement for cryptographic tasks involving several users.

(arXiv:2111.05363)


Room P5.18, Mathematics Building

Gilles Brassard

Gilles Brassard, Université de Montréal
Computable versus printable numbers

Even though mathematics may seem universal, this is not the case. Constructive mathematics, whose main proponent was Brouwer, offers a radically different perspective compared to classical mathematics rooted in the logic of Aristotle. In this talk, I shall discuss various definitions of computable reals and computable functions. We shall see that a definition of computable reals that appears very natural make multiplication by 3 uncomputable.