Towards a direct, precision measurement of the quantum vacuum Lagrangian coupling coefficients with super-intense counterpropagating pulses

A possible experimental scenario for direct, precision measurement of the two coupling coefficients of the QED Lagrangian via photon-photon scattering will be presented. Such a measurement, which would not depend on the quantum vacuum (qvac) being birefringent, could be made using a super-intense pump beam to prepare the qvac and a moderately-intense counterpropagating probe beam to scatter photons as they traverse the excited qvac. We will discuss key conditions (e.g., pulse widths, beam waists, spatial profiles, the state of the physical vacuum, etc.) that would render the scattered photons detectable above the noise. Numerical simulations will be presented [1], which show an experiment of this nature is barely feasible at intensities of 10²³ W/cm² and most promising at 10²⁴ W/cm², prior to the breakdown of the qvac at higher intensities.



[1] L. Roso, et al., New J. Phys. 24, 025010 (2022).