Past Events

Continuous-time quantum walks in graphs

on 08-02-2019

Gabriel Coutinho, from the Federal University of Minas Gerais, Brasil

Date & time: Friday, February 8th, 14:30h
Location: Instituto Superior Técnico, Lisbon, Room 2.8.11, Physics Building

Quantum walks have been around for some time now, and there are just too many questions one could ask about them. In this talk, I shall focus on questions related to transport tasks in qubit networks modelled by simple graphs. We eventually hope to have a full understanding on how exactly the combinatorics of the graph might affect the quantum properties, but we will see that we are still very far away from achieving this goal — even for very simple questions. More Information..

Quantum-Proof Blockchain

on 18-01-2019

Jintai Ding, from the Department of Mathematics of the University of Cincinnati

Date & time: Friday, January 18th, 16:00h - 17:00
Location: Instituto Superior Técnico, Lisbon, Room P3.10, Mathematics Building

Blockchain technology is now going through explosive development with the aim to build a new generation of revolutionary financial technology. The most successful example is new digital currency bitcoin. The fundamental building block in blockchain technology is actually cryptographic algorithms, which is why bitcoin is actually called a cryptocurrency. The main cryptographic algorithms used in blockchain technology are hash functions and elliptic curve digital signatures. As we all know, quantum computers are not such a significant threat to the security of Hash functions but it can be fatal to the elliptic curve digital signatures. In this presentation, we will first show how the quantum computers can threat the security of blockchain technology, in particular, why the existing blockchain technology used in bitcoins can not fundamentally avoid such a practical attack. Then we will explain the challenges we will face if if we just plug in existing post-quantum cryptographic solutions as a drop-in to replace the existing elliptic curve signatures, in particular, the key size problem and a few others. In the end, we will present some of the new solutions we have been developing to deal with these fundamental problems including a new type of proof of work algorithms, which, we believe, provide very viable solutions for the future long term secure blockchain technology.
More Information..