2018 LOGICAL qubits would break current crypto.
But qubits decohere extremely fast, so you need error correcting schemes. Current estimates require 1000 - 10000 physical qubits per logical error corrected qubit.
No, no one cares about those HW problems. To break RSA keys you need 0 error correction. You only need >2000 entangled qbits, and they either produce a correct result or not.
For other calculations you might need error correction, but this leads to nowhere with current technology.
What the Chinese did was groundbreaking.
For other calculations you might need error correction, but this leads to nowhere with current technology. What the Chinese did was groundbreaking.