  We explore the implications of the QCD phase transition during the postbounce
evolution of core-collapse supernovae. Using the MIT bag model for the
description of quark matter and assuming small bag constants, we find that the
phase transition occurs during the early postbounce accretion phase. This stage
of the evolution can be simulated with general relativistic three-flavor
Boltzmann neutrino transport. The phase transition produces a second shock wave
that triggers a delayed supernova explosion. If such a phase transition happens
in a future galactic supernova, its existence and properties should become
observable as a second peak in the neutrino signal that is accompanied by
significant changes in the energy of the emitted neutrinos. In contrast to the
first neutronization burst, this second neutrino burst is dominated by the
emission of anti-neutrinos because the electron-degeneracy is lifted when the
second shock passes through the previously neutronized matter.
