Time reversed states in barrier tunneling

Tunneling, though a physical reality, is shrouded in mystery. Wave packets cannot be constructed under the barrier and group velocity defined. The tunneling particle can observed on either side of but its properties has never been probed due to several problems related quantum measurement. We show that there are ways bypass these mesoscopic systems one even derive an expression for mechanical current barrier. A general scheme developed this any arbitrary system. One use phenomena subject theoretical experimental cross checks. For demonstration we consider ideal 1D ring with Aharonov–Bohm flux Φ, connected reservoir. It gives clear evidence propagation occur resulting measured non-invasively theoretically checked. Time reversed states play role no violation causality. evanescent known largely stable robust against phase fluctuations making them possible candidate device applications so formalizing important.