Overall Objectives
Research Program
Application Domains
Highlights of the Year
New Software and Platforms
New Results
Bilateral Contracts and Grants with Industry
Partnerships and Cooperations
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Section: New Results

Quantum Information

Participants : Xavier Bonnetain, Rémi Bricout, Kaushik Chakraborty, André Chailloux, Shouvik Ghorai, Antoine Grospellier, Anirudh Krishna, Gaëtan Leurent, Anthony Leverrier, Vivien Londe, María Naya Plasencia, Andrea Olivo, Jean-Pierre Tillich, Sristy Agrawal, André Schrottenloher.

Our research in quantum information focusses on several axes: quantum codes with the goal of developing better error correction strategies to build large quantum computers, quantum cryptography which exploits the laws of quantum mechanics to derive security guarantees, relativistic cryptography which exploits in addition the fact that no information can travel faster than the speed of light and finally quantum cryptanalysis which investigates how quantum computers could be harnessed to attack classical cryptosystems.

Quantum codes

Protecting quantum information from external noise is an issue of paramount importance for building a quantum computer. It also worthwhile to notice that all quantum error-correcting code schemes proposed up to now suffer from the very same problem that the first (classical) error-correcting codes had: there are constructions of good quantum codes, but for the best of them it is not known how to decode them in polynomial time.

Recent results:

Quantum cryptography

Quantum cryptography exploits the laws of quantum physics to establish the security of certain cryptographic primitives. The most studied one is certainly quantum key distribution, which allows two distant parties to establish a secret using an untrusted quantum channel. Our activity in this field is particularly focussed on protocols with continuous variables, which are well-suited to implementations. Another primitive is quantum money and was in fact the first proposed idea of quantum cryptography in the 70s. However, this primitive hasn't received much attention because its implementation requires quantum memories, which weren't available until now.

Recent results:

Relativistic cryptography

Two-party cryptographic tasks are well-known to be impossible without complexity assumptions, either in the classical or the quantum world. Remarkably, such no-go theorems become invalid when adding the physical assumption that no information can travel faster than the speed of light. This additional assumption gives rise to the emerging field of relativistic cryptography. We worked on this topic for several years and Andrea Olivo was recruited as a PhD student to continue working on both theoretical and practical aspects of relativistic cryptography.

Recent results:

Quantum cryptanalysis of symmetric primitives

Symmetric cryptography seems at first sight much less affected in the post-quantum world than asymmetric cryptography: its main known threat seemed for a long time Grover's algorithm, which allows for an exhaustive key search in the square root of the normal complexity. For this reason, it was usually believed that doubling key lengths suffices to maintain an equivalent security in the post-quantum world. However, a lot of work is certainly required in the field of symmetric cryptography in order to “quantize” the classical families of attacks in an optimized way, as well as to find new dedicated quantum attacks. M. Naya Plasencia has recently been awarded an ERC Starting grant for her project named QUASYModo on this topic, that has started on september 2017.

Recent results: