I'm a postdoc researcher in quantum cryptography at CWI/QuSoft in Amsterdam. I'm co-supervised by Stacey Jeffery, Christian Schaffner and Florian Speelman.

Expertise

While I'm interested in quantum computing and cryptography in general, my research mostly focuses on delegated quantum computing and quantum multiparty computing (MPC).

I notably worked on the design and security analysis of protocols related to delegated blind quantum computing assuming a purely classical client, involving lattice based cryptography and composable security. More recently I started to get interested in many other problems, including the generalization of Zero-Knowledge proofs to quantum states and their applications to MPC, the composable distribution of graph states, one-time memories, ZX-calculus and more.

Curriculum

I studied at the Ecole Normale Supérieure (ENS) Paris-Saclay, which is part of the Université Paris-Saclay. I have two bachelors (in physics and computer science) and a master in computer science (MPRI). I did my PhD in Sorbonne Université, supervised by Elham Kashefi and Antoine Joux. For more details, see my CV.

Research

Among others, I worked on the design and security proof of QFactory, a protocol that can be used to prepare a quantum state on a server in such a way that the purely classical client knows the description of that state while this state is unknown to the server.

This primitive is a fundamental building block in many protocols, allowing for example blind delegated quantum computation. The construction of QFactory involves careful design of cryptographic functions based on the Learning With Errors (LWE) problem.

I also showed impossibility results regarding composable security of classical-client Remote State Preparation protocols and classical-client Universal Blind Quantum Computing protocols.

I am now notably developing an extension of Zero-Knowledge to quantum states and I study their applications to multiparty computing. In parallel, I work on numerous other projects, involving in particular composable graph state preparation, one-time memories, ZX-calculs…


Teaching

I have been a teaching assistant in Sorbonne Université and Universiteit van Amsterdam:

  • Python (L2)
  • Cryptography (L3)
  • Discrete Mathematics (L2)

In particular, I have been exploring the benefit of flipped-classroom with Christian Schaffner.

I also tutored a student during 4 years to successfully prepare him to some very important and competitive national exams in Israel. Among others, I taught him advanced assembly (creating our own compiler and a basic OS from scratch) and basics of machine learning applied to opinion mining.


Hobbies

I am a fan of Salsa since I discovered it in 2012. I was the head of a Salsa association in 2015−2016, and for two years I co-created Salsa choreography shows. I also like music in general: I played the Piano for 9 years, and I started to learn the Saxophone in 2018.

I also really like programming in my free time, and I enjoy exploring this wonderful world. Of course, I'm a strong supporter of the open source community (NixOs ).

And finally, I like Nature. Hiking, biking, photography, travelling (locally if possible: too bad plane is not carbon-friendly…), and, without forgetting my first love: astronomy!

Hopefully, I'll soon be able to talk about all of that (and more) in my blog!


Latest News

Several people asked me for the slides I made for the Quantum Introductory Tutorial at the Spring School in Theoretical Computer Science (EPIT). You can find them here (with the PDF and short animations).

Publications and Preprints

Papers are listed in reverse order, based on their first online appearance. See also my Google Scholar profile.

  • Non-Destructive Zero-Knowledge Proofs on Quantum States, and Multi-Party Generation of Authorized Hidden GHZ States
    L. Colisson, F. Grosshans, E. Kashefi
    Manuscript, arXiv:2104.04742, April 2021.
  • Security Limitations of Classical-Client Delegated Quantum Computing
    C. Badertscher, A. Cojocaru, L. Colisson, E. Kashefi, D. Leichtle, A. Mantri, P. Wallden
    ASIACRYPT 2020 (Video, Short live session), Presented at Q-turn 2020, arXiv:2007.01668, July 2020.
  • QFactory: classically-instructed remote secret qubits preparation
    A. Cojocaru, L. Colisson, E. Kashefi, P. Wallden
    ASIACRYPT 2019, arXiv:1904.06303, April 2019.
  • On the possibility of classical client blind quantum computing
    A. Cojocaru, L. Colisson, E. Kashefi, P. Wallden
    Cryptography 2021 (Selected for the Journal Issue Cover), Presented at QCrypt2018 (Video, Slides), arXiv:1802.08759, February 2018.

Invited Talks

  • Tutorial: Basics of quantum information (3h)
    Spring School EPIT 2021 (Slides), 24-28 May, 2021.
  • Non-Destructive Zero-Knowledge Proofs on Quantum States, and Multi-Party Generation of Authorized Hidden GHZ States
    Quantum Information Theory Seminar, UCL, 1 July, 2021.

International Conference Talks

  • Security Limitations of Classical-Client Delegated Quantum Computing
    C. Badertscher, A. Cojocaru, L. Colisson, E. Kashefi, D. Leichtle, A. Mantri, P. Wallden
    Speaker at ASIACRYPT 2020 (Video, Short live session).
  • On the possibility of classical client blind quantum computing
    A. Cojocaru, L. Colisson, E. Kashefi, P. Wallden
    Speaker at:
    • QCrypt 2018, Shanghai, China (Video, Slides),
    • JIQ 2018, Nancy, France.

Posters

  • Security Limitations of Classical-Client Delegated Quantum Computing
    C. Badertscher, A. Cojocaru, L. Colisson, E. Kashefi, D. Leichtle, A. Mantri, P. Wallden
    Poster at QCrypt 2020
  • On the possibility of classical client blind quantum computing
    A. Cojocaru, L. Colisson, E. Kashefi, P. Wallden
    Poster at:
    • GdR-IQFA 2018, Montpellier, France,
    • ICoCQ 2018, Paris, France.

PhD thesis

You can download my PhD thesis here.

Internship Reports

  • Calcul quantique délégué à l'aveugle par un client classique
    L. Colisson
    Master 2 Internship Report (supervised by Céline Chevalier between March 2018 and July 2018).
  • Classically Driven Delegated Blind Quantum Computing
    L. Colisson
    Master 1 Internship Report (supervised by Elham Kashefi between February 2017 and July 2017).
  • Quantum Analog of Differential Privacy in Term of Rényi Divergence
    L. Colisson
    License 3 Internship Report (supervised by Omar Fawzi in June 2016).