So by a "tremendous boon to cryptocurrency mining" you actually mean completely disastrous to all known cryptocurrencies. It will be interesting to see if some

So by a "tremendous boon to cryptocurrency mining" you actually mean completely disastrous to all known cryptocurrencies. It will be interesting to see if someday the prospect of effective quantum computers has a definite economic effect on the value of bitcoin or its successors. I don't imagine currencies work very well when they have an expiration date.