“…Accounts of this debate can be found in a large number of reviews (see de Carvalho and Nussenzveig, 2002;Hauge and Støvneng, 1989;Landauer and Martin, 1994;Olkhovsky et al, 2004;Winful, 2006;Muga et al, 2007;Choi and Jordan, 2013). As a well-defined operator whose eigenvalue would correspond to the travel time through the classically forbidden region could not be identified, unconventional operational descriptions have been put forward, such as complex travel time based on a Feynman path integral formulation (Sokolovski et al, 1994) or contextual values replacing conventional eigenvalues of a self-adjoined operators for so-called weak measurements (Choi and Jordan, 2013). Closely related is the notion of a Larmor clock (Baz', 1967a,b;Büttiker, 1983) which yields, in general, two different precession times which can be interpreted in special cases as the real and imaginary parts of a complex time (Sokolovski et al, 1994).…”