I'm a PhD student in quantum cryptography at the LIP6 laboratory (Laboratoire d'Informatique Paris 6) of Sorbonne Université (France). I'm supervised by Prof. Elham Kashefi and Prof. Antoine Joux.

Expertise

I'm working mostly on the design and the security analysis of protocols related to delegated blind quantum computing, assuming a purely classical client. I use notably lattice based cryptography and composable security.

Curriculum

After two years of highly intensive competitive exam preparation, I had the chance to enter the Ecole Normale Supérieure (ENS) Paris-Saclay, itself part of the Université Paris-Saclay. After completing a first Bachelor in physics, I obtained a second Bachelor and a Master in computer science (MPRI). Fore more information, see my CV.

Research

I worked mostly 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.


Teaching

I have been a teaching assistant in:

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

I'm also tutoring a student since 2017 (he is in 2020 starting his first year at the university) to prepare him for some very important and competitive national exams in Israel. I taught him notably:

  • Programming, including Functional and Object-Oriented Programming (Python/Django, Javascript, C, Ocaml…)
  • Assembly: creation of a compiler in Ocaml to compile a "C--" language into 64 bits assembly
  • System Architecture: he started to create a basic OS from scratch, booting in real 16 bits mode
  • AI: he is now starting a project on opinion mining, that should involve Machine Learning, SVM…


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.

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.