All hashcash based PoW, including bitcoin's, is subject to quantum speedup by Grover's search algorithm. It allows you to find a hash output with 80 leading zer

All hashcash based PoW, including bitcoin's, is subject to quantum speedup by Grover's search algorithm. It allows you to find a hash output with 80 leading zero bits in roughly 2^40 steps rather than the 2^80 steps classically needed.