The best-known tmto algorithm is 20 million times slower with 1 millionth' the memory.
Of course, even being just 200 times slower means you will rarely find a block
if the block interval is just 100 proof attempts long...
This is where we stopped the last time - I claimed that it's not a problem for a QC to do 20 million computations at once (25X qubits is enough to do a computation on 33 million sets of data).
It is a big misconception to think that QC are some magical device that can speedup arbitrary computation. Evidence suggests that they have limited speedup applicability
(all variations of Grover's unstructured search and Shor's group structured search).
I think I urged you to read Scott Aaronson's
"The Limits of Quantum Computers"
http://www.scottaaronson.com/writings/limitsqc-draft.pdflast time, to correct this misconception.