The fundamental problem Penrose identifies boils down to the halting problem, which requires a halting oracle to be solved. Hence, a halting oracle is the best explanation for the human mind, and no form of computation, quantum or otherwise, suffices.
UPDATE:
Since I'm rate limited, here is my answer to the replier's comment:
A partial answer: the mind has access to the concept of infinity, and can identify new, consistent axioms. Other possibilities: future causality and ability to change the fundamental probability distribution.
But, it's also important to note that we don't have to answer the "how" question in order to identify halting oracles as a viable explanation. We often identify new phenomena and anomalies without being able to explain them, so the identification is a first step.