[regularfry]

At this point my bet is that the breakthrough isn't going to be qbits per chip, it's going to be entanglements-per-second in quantum networking. If you could string together simpler processors in a cluster at anything approaching interesting scales then all of a sudden the orders of magnitude become a lot less constrained and it's just a money problem.

[freetonik]

Quantum networking is a lesser problem than changing the state and keeping intact long enough. You can already move quantum state over fiber optics pretty reliably, so transport exists, but what then? You need to put the qubits of the connected chip into the corresponding state (which takes time), and do it many times, and all that time is an overhead.

Superconducting QCs are fast, but the state degrades incredibly quickly, so you only have a fraction of a second (maybe a millisecond at best, currently) until the entire state is garbage. Some other modalities like trapped ion are the opposite: state can live long, but each operation is orders of magnitude slower.