Rhodopsin, in our retina, exploits a quantun mechanical effect. You could argue that our brains are quantum computers if you consider our retina including rhodopsin to be part of the brain.
Anything and everything is because of quantum mechanics, sure. But you could've asked a classical physicist to design an apple "computer" (the fruit)— just arrange the right atoms— but you couldn't have asked a classical physicist to design a retina computer exploiting rhodopsin.