I like the possibility of QC in brain. However, explaining why brain is much more efficient that computers does not need QC. Computers and Brain evolved in two completely different ways. For the brain, simple cognitive functions emerge first, supporting more complex life behaviours, starting with very simple multi celular life forms. Logical reasoning emerges much later, and is pretty expensive. Then we made computers to do logical computation and they are incredibly efficient at it: a modern low power processor is much more efficient than human brain in this kind of workload, by orders of magnitude.

Now we are trying to implement what the mind is naturally good at with systems designed to do logic well. This is the main reason it's so inefficient. Emulation is costly. It is costly when brain does logic, and is costly when computers do AI.

In theory, we should be able to build computing devices designed for AI workloads, and they can be as efficient as brain or even much better.