  A single wave component of a quantum particle can in principle be detected by
the way that it interferes with itself, that is, through the local wave
function correlation. The interpretation as the expectation of a local
translation operator allows this measure of quantum wavyness to be followed
through the process of decoherence in open quantum systems. This is here
assumed to be Markovian, determined by Lindblad operators that are linear in
position and momentum. The limitation of small averaging windows and even
smaller correlation lengths simplifies the semiclassical theory for the
evolving local correlation. Its spectrum has a peak for each classical
momentum, subjected to Gaussian broadening with decoherence. These spectral
lines can be clearly resolved even after the Wigner function has become
positive: The correlations located far from caustics seem to be the last
vestige of quantum oscilations.
