Characteristic time-scales for macroscopic quantum tunneling

Tunneling time (τt ), in its real and imaginary parts, can be deduced from measurements of decay time (τd ) in Josephson junctions. It turns out that the real part of τt is much shorter than the imaginary one, which can be identified with the semiclassical time. A third quantity is the Zeno-time (τZ) which, in turn, can be estimated from the previous ones, since it is approximately given by their geometrical mean. The possibility of observing the Zeno-effect is then discussed.