  We revisit the notions of the quantum-mechanical sojourn time in the context
of the quantum clocks to enquire whether the sojourn time be clocked without
the clock affecting the dynamics of the wave motion. Upon recognizing that the
positivity of conditional sojourn time is not ensured even in the case of
physically co-evolving clock mechanisms, we trace its origins to the
non-trivial inadvertent scattering arising from the disparity, however weak,
engendered by the very clock potential. Specifically, our investigations focus
on the Larmor spin rotation-based unitary clock where the alleviation of these
unphysical contributions has been achieved by correcting the mathematical
apparatus of extracting the sojourn times. The corrections have been obtained
for both the spin precession-based and spin alignment-based scenarios. The
sojourn times so obtained are found to have proper high- and low-energy limits
and turn out to be positive definite for an arbitrary potential. The regimen
provided here is general and appeals equivalently for unitary as well as
non-unitary clocks where the clock-induced perturbations couple to the system
Hamiltonian.

Quantum Physics