Quantun Tunneling

Most recent answer: 10/22/2007

Q:
How come when I use quantum mechanics to find the probability of an individual atom tunneling through a barrier and multiply the probability by itself n times (for n atoms) to obtain the probability of n atoms tunneling through a barrier, it’s not equal to the probability of a mass consisting of n atoms tunneling through the same barrier?
- Jim (age 20)
University of Pittsburgh
A:
That’s a nice question.
I assume you mean probability in some fixed time interval. When you stop and think about it, even for a similar classical problem there would be no reason for two probabilities like that to be equal. They correspond to genuinely different physical processes. In one case, the atoms leak across at a variety of different times. In the other case, they move across together as a coherent block. Classically, the chance the all the water molecules in a glass will hop out of the glass (i.e. evaporate) can be very high even though the chance that they all hop out together is very low indeed.

mike w

(published on 10/22/2007)