# Signal coherence/correlation vs quantum coherence

In general, I understand a signal $$s(t) \in \mathbb{C}$$ is called "coherent" when it has a large autocorrelation function. A pair of different signals $$s(t)$$, $$r(t)$$ can also be "coherent" if their cross-correlation is large (this can be made precise). I also understand a bit of the density matrix formalism $$\rho$$ in quantum mechanics and what is meant by quantum coherence.

However, I fail to see a clear mathematical connection between the two, beyond some phenomenological similarities when talking about "waves". Could anyone shed some light on it?