Some quantum systems are so complex, especially when the number of degrees of freedom to describe increases, that their simulation on classical computers is impossible. For this complex quantum systems “Let the computer itself be built of quantum mechanical elements which obey quantum mechanical laws” (R. Feynman, 1982).

Quantum simulations of interacting many-body systems in condensed matter, chemistry, atomic, nuclear or particle physics may potentially bring us to address so-called ‘Grand Challenge’ problems, i.e. problems that cannot be tackled using classical computation. In particular, quantum computing may provide the possibility to work with Hilbert space dimensionalities that are exponentially larger than those accessible with classical computers, thus overcoming the limitations that are currently preventing the exact theoretical many-body description of large and complex systems. First concrete steps in this direction have been made in the past few years in quantum chemistry and condensed matter. One of the goals of the QC2I project is to apply quantum technology in the context of the nuclear many-body problem, with three specific objectives:

- test the pertinence of state of the art algorithms and methods, mainly developed in other fields, in nuclear and particle physics applications,
- design new algorithms tailored to nuclear or particle systems,
- investigate the possible feedback of nuclear or particle physics approaches to quantum simulations of other interacting many-body systems.

These objectives will be achieved by combining our accumulated expertise in the many-body problem with the latest advances in quantum algorithms.

(**ended december 2022**)