NP-QED — Sonder la frontière non perturbative de l'électrodynamique quantique

Quantum Electrodynamics (QED) is the theory that unifies electromagnetism and quantum mechanics to describe how light and charged particles interact. Considered as one of the most accurately tested theories, it led Richard Feynman to call it “the jewel of physics”. Yet, in its strong-field (SF) regime, when the light fields E are ultra-intense and close to the so-called Schwinger limit (ES>10^18V/m) in the charged particles rest frame, QED has so far remained ‘terra incognita’ in experiments and the developed SF-QED theory has never received an accurate experimental validation. When the electric field is well above the Schwinger limit (E>1600 ES) in the particles rest frame, QED enters the so-called ‘fully non-perturbative regime’ (NP), for which there is currently no accepted theory to describe how light interact with charged particles. Due to the extreme fields values required, the SF and NP regimes of QED are out of the reach of all experiments envisaged so far with current high-power laser technology, that currently offers the most intense source of electric field on earth. To break this barrier, we propose a new approach based on so-called Doppler-boosted lasers, than rely on plasma optical devices dubbed 'plasma mirrors' to considerably boost the intensity of current lasers by orders of magnitude. By colliding such Doppler-boosted lasers with relativistic electron beams produced by laser-plasma accelerators, it could in principle be possible to reach the fully NP regime of QED. The implementation of such experiment is very ambitious, requires many complementary expertise (strong-field quantum electrodynamics, Doppler-boosting with plasma mirrors, high-intensity laser-matter modelling, laser-plasma acceleration and electron beam manipulation, laser and electron beam spatio-temporal characterization) and considerable funding. In this context, we plan to apply for an ERC synergy grant for the upcoming call. We recently set-up an international consortium of three principal investigators and are in the phase of writing the proposal. The present ANR project would help us support our consortium (on-site meetings and brainstorming) as well as finalizing the writing of our proposal (external ERC expert consultant).