What do quantum particles do, being under potential barrier? Tunnelling   time. A Virtual Experiment Standpoint
  Addressed, mainly: postgraduates and related readers. Subject: Given two classical mechanical 1D-moving particles (material points), with identical initial data, one of those particles given free and another given to pass through a symmetrical force-barrier, a retardation effect is observed: After the barrier has been passed over, the second particle moves with the same velocity as the free particle, but spacially is retarded with respect to the latter. If the "non-free" particle moves through a potential well, then the retarded particle is the free particle. The question is. What phenomena of a similar kind could one find, if the 1D-moving particles were quantum ones? And just what do quantum particles do, being under potential barrier? I here say "quantum" in a mathematical sense: "Schroedinger". To answer the question, I had constructed some suitable Virtual Devices (Java applets) and then for some time experimented various situations. Some of those Java applets are available at "http://choroszavin.narod.ru/vlab/index-2.htm" 
Sergej A. Choroszavin