Sure, but it's designed to minimize the chance that a quantum fluctuation could change the outcome of a computation, right? Whereas in the brain that might not be the case. A lot of the "interesting" neural activity (e.g. relating to decision making, language, etc) happen in highly sensitive dynamical regimes: on a threshold of firing, or activating one neural population vs another. (Arguably you can get the same effect in an artificial network by adding true random noise though!)