It is a question of efficiency, our brains run on about 15 Watts.
Quantum computers offer many orders of magnitude of efficiency by a (handwavy) 'searching the whole solution space' sort of ultimate parallelism.
The new field of Quantum Biology[1] shows that many biological processes exploit quantum effects, e.g. enzymes exploiting quantum tunelling to unknot proteins, robin's direction sense, photon pathfinding to reaction centre in photosynthesis.
It is therefore not entirely unlikely that brain's exploit various quantum effects to make thinking much more efficient.