  We investigate electron-positron pair production from vacuum for short laser
pulses with sub-cycle structure, in the nonperturbative regime (Schwinger pair
production). We use the non-equilibrium quantum kinetic approach, and show that
the momentum spectrum of the created electron-positron pairs is extremely
sensitive to the sub-cycle dynamics -- depending on the laser frequency
$\omega$, the pulse length $\tau$, and the carrier phase $\phi$ -- and shows
several distinctive new signatures. This observation could help not only in the
design of laser pulses to optimize the experimental signature of Schwinger pair
production, but also ultimately lead to new probes of light pulses at extremely
short time scales.
