It was shown after the original proposal in 2012 that these signatures can only be observed in "non-equilibrium" systems, so we are actually supplying the pulses, which drive the ticking. The quantum basis for the robust frequency of the ticking relies on dipole-dipole interactions among the nuclear spins.

It is very difficult to understand the complex state of the system after many of these interactions, but in our papers we explore how "coherent" the interactions are by "resurrecting" the signal in what are called spin echoes [1]. Simply speaking, after many interactions the "order" of the system lies not in the nuclear spins individually, but in a complex network of interactions among the spins -- this complex order is not observable (and so the signal appears to "decay away" over time).

Using techniques developed in nuclear magnetic resonance (NMR), we are able to put this "order" back into an observable state, and watch it return. It feels like reversing time, I never get used to it!

[1] https://en.wikipedia.org/wiki/Spin_echo