Characteristic time-scales for macroscopic quantum tunneling

Tunneling time (taut), in its real and imaginary parts, can be deduced from measurements of decay time (taud) in Josephson junctions. It turns out that the real part of taut is much shorter than the imaginary one, which can be identified with the semiclassical time. A third quantity is the Zeno-time (tauz) 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.