If blockchain is a public ledger which stores all of the transactions that have occurred and will occur , would it better to merge both quantum cryptography and blockchain together to store immutable data instead of using something like a directed acyclic graph? (DAG)
Can you please explain, what do you mean by quantum cryptography?
To answer your question, the algorithm that can do integer factorization on a quantum computer has not been successfully applied and quantum computing is very far from being available to regular people.