### Speaker

Prof.
Beom Jun Kim
(Sungkyunkwan University)

### Description

We study time-reversal dynamics of quantum diffusion in the
Watts-Strogatz small-world networks at the rewiring
probability $p$. We start from the localized wave packet,
and integrate the time-dependent Schr\"odinger equation. At
time $T$ a perturbation to the wave packet is made and then
the system evolves backward in time until $t=2T$ is reached.
We calculate the mean square displacement $\sigma(t; \eta)$
of the wave packet as a function of time $t$ at different
perturbation strength $\eta$. The time irreversibility is
quantitatively measured by $\sigma(2T; \eta) - \sigma(2T;
0)$, which reveals that the irreversibility linearly
increases with $\eta$ in the weakly perturbed regime. The
results from the WS networks and the regular network are
compared.