Tunneling time, the barrier time-delay and weak measurement What was or can actually be measured with the Attoclock?

The measurement of the tunneling time-delay in attosecond experiments, termed attoclock, despite its controversies, offers a fruitful opportunity to understand the tunneling time and the tunnel-ionization process. In previous work, we showed a model that well describes the time-delay measured by the attoclock experiment in the adiabatic and nonadiabatic field calibrations. In the present work we show that the tunneling time reveals a universal behavior, with disentangled contribution, where the barrier time-delay can be convincingly defined and determined from the difference between the time-delay of adiabatic and nonadiabatic tunnel-ionization, with good agreement with the experimental result. Furthermore, we show that in the weak measurement limit, the barrier time-delay corresponds to the Larmor-clock time and the interaction time within the barrier.