  Quantum vacuum fluctuations give rise to effective non-linear interactions
between electromagnetic fields. A prominent signature of quantum vacuum
nonlinearities driven by macroscopic fields are signal photons differing in
characteristic properties such as frequency, propagation direction and
polarization from the driving fields. We devise a strategy for the efficient
tracing of the various vacuum-fluctuation-mediated interaction processes in
order to identify the most prospective signal photon channels. As an example,
we study the collision of up to four optical laser pulses and pay attention to
sum and difference frequency generation. We demonstrate how this information
can be used to enhance the signal photon yield in laser pulse collisions for a
given total laser energy.
