I understand that if a particle approaches a finite potential barrier of height $V_0$ with energy $E < V_0$, there is still a finite probability of finding the particle on the other side of the barrier due to quantum tunneling.
My question is, since the wavefunction is nonzero inside the barrier region, is it possible to actually make a position measurement and locate a particle inside the barrier?
I mean, if we can say that "there is a nonzero probability that the particle is inside the barrier", surely this would suggest we can do so?
If not, why not? Am I understanding the whole wavefunction/probability distribution thing right?
Best Answer
Yes you appear to "understand the whole wavefunction / probability distribution thing right", and it is possible to measure a probability of presence in the forbidden region, but this probability is usually small.
I don't know whether any experiment has shown it with "real particle" like atoms, electrons or neutron, but it has been definitely shown with photons. The "classically forbidden region" in the particle pictures corresponds to evanescent waves, and there have been experiment where evanescent waves have been used to excite the fluorescence of atoms. Each photon emitted by an atom in the evanescent wave can then be seen as a position measurement of a photon in the evanescent wave region.