  We statistically study vortex reconnections in quantum fluids by evolving
different realizations of vortex Hopf links using the Gross--Pitaevskii model.
Despite the time-reversibility of the model, we report a clear evidence that
the dynamics of the reconnection process is time-irreversible, as reconnecting
vortices tend to separate faster than they approach. Thanks to a matching
theory devised concurrently in Proment and Krstulovic (arXiv:2005.02047), we
quantitatively relate the origin of this asymmetry to the generation of a sound
pulse after the reconnection event. Our results have the prospect of being
tested in several quantum fluid experiments and, theoretically, may shed new
light on the energy transfer mechanisms in both classical and quantum turbulent
fluids.
