You cannot steal bitcoins from an address that's never been spent, since you only know the hash of the public key. There are about 2^256/2^160=2^96 possible fu

You cannot steal bitcoins from an address that's never been spent, since you only know the hash of the public key. There are about 2^256/2^160=2^96 possible full public keys mapping to the known key hash, so you could run Grover's algorithm to recover one in about sqrt(2^96)=2^48 steps, but given the slow cycle time of quantum computers, that's still going to be infeasible for a long time. This is why address re-use is not recommended...