According to quantum tunnelling an electron takes every possible path?

Reading Brian Green's book - the elegant universe - he mentions that when Heisenberg was toying With the uncertainty principle he encountered quantum tunnelling where positrons and/or electrons have no exact position and momentum that can be measured. But i thought penning traps did just that? If so, how did penning trap electrons and indeed anti-matter for upto a week if it's exact location AND velocities cannot be measured?

Edited October 20, 201114 yr by hawksmere

Penning traps don't measure exact locations. The confined articles are not stationary — they are moving in an orbit and you can determine oscillation frequencies quite precisely, so you can make spectroscopic measurements. But that does not require exact position information.