  We discuss the interplay of wave packet decoherence and decoherence induced
by quantum gravity via interactions with spacetime foam for high energy
astrophysical neutrinos. In this context we point out a compelling consequence
of the expectation that quantum gravity should break global symmetries, namely
that quantum-gravity induced decoherence may not only be the most sensitive
probe for quantum properties of spacetime, but also can provide both a powerful
tool for the search for new particles, including totally decoupled backgrounds
interacting only gravitationally, and at the same time a window into the
intricacies of black hole information processing.
