Quantum Vacuum at High Intensity
In classical physics, the vacuum describes a completely empty space free of any matter. However, quantum physics predict the presence of virtual particle-antiparticle pairs constituting the quantum mechanical ground state of the vacuum.
Photons of an electromagnetic wave can couple to these virtual pairs of charged particles, effectively making the vacuum a nonlinear optical medium (vacuum polarization, vacuum birefringence).
With sufficient photon energy or field strength, the virtual charges may even be separated and made real, thus creating matter purely from radiation in vacuum (pair production).
While the field strengths at which these effects become significant are extremely high, the increasing availability of high-power laser facilities in the Petawatt class and their unique ability to create extreme fields may push the tiny interaction probabilities for these so-called “quantum vacuum” effects into a measurable region for the first time.
In the framework of the DFG research unit “Probing the quantum vacuum” (http://quantumvacuum.org/) two projects are being pursued at CALA:
• Multiphoton Breit-Wheeler pair production
• Photon-photon scattering