I spent the evening looking into quantum computing timelines as a non-expert in quantum computing. Here is what I’ve learned:
We currently have machines with ~1,000–1,500 physical qubits at error rates around 10⁻³, and Google’s algorithm requires ~500,000 physical qubits operating coherently together with surface code error correction, yoked qubit storage, magic state cultivation producing ~500K T states per second, and reaction-limited execution at 10μs cycle times — none of which has been demonstrated beyond small-scale proof-of-concept experiments.
Scaling from where we are to where this needs to be isn’t a matter of incremental improvement along a Moore’s Law curve; it requires solving qualitatively new engineering problems in qubit fabrication yield, correlated error suppression across a massive chip (or multi-chip interconnects that don’t exist yet), cryogenic wiring and control electronics for half a million qubits, real-time classical decoding at the required throughput, and sustained coherence of a “primed” quantum state across minutes of wall-clock time — any one of which could prove to be a multi-year bottleneck, and all of which must be solved simultaneously.
Given the above, I just don’t see how we’re going to get to a cryptographically relevant quantum computer by 2030, especially given that we need a ~350× increase in physical qubit count with simultaneously tighter error correlations, an entirely new cryogenic control and wiring architecture to address half a million qubits, real-time decoding infrastructure that doesn’t exist yet, magic state distillation factories operating at industrial throughput, and multi-minute coherent idle times for primed states — and historically, solving even one of these at scale has taken the field the better part of a decade.