There are technologies that would not need the 15mK operating temperatures, they are just in their infancy.
The most interesting applications of quantum computing have little to do with encryption or breaking codes. Chemistry and optimization problems are much more exciting.
SHA-256 is a hash, not an encryption algorithm. And quantum computers have nothing to contribute to reversing hashes or breaking symmetric encryption.
While I don't doubt that advances are being made, this has the hallmarks of cold fusion all over again. By the time it is in production, DeepMind will have made significant head way using conventional CPU/GPU.
The most interesting applications of quantum computing have little to do with encryption or breaking codes. Chemistry and optimization problems are much more exciting.
SHA-256 is a hash, not an encryption algorithm. And quantum computers have nothing to contribute to reversing hashes or breaking symmetric encryption.