  According to a basic rule of fermionic and bosonic many-body physics, known
as the linked cluster theorem, physical observables are not affected by vacuum
bubbles, which represent virtual particles created from vacuum and
self-annihilating without interacting with real particles. Here, we show that
this conventional knowledge must be revised for anyons, quasiparticles that
obey fractional exchange statistics intermediate between fermions and bosons.
We find that a certain class of vacuum bubbles of Abelian anyons does affect
physical observables. They represent virtually excited anyons which wind around
real anyonic excitations. These topological bubbles result in a
temperature-dependent phase shift of Fabry-Perot interference patterns in the
fractional quantum Hall regime accessible in current experiments, thus
providing a tool for direct and unambiguous observation of elusive fractional
statistics.
