Research seriesL3algorithms
How many qubits, for how long, and by when — Shor and Grover derived from scratch, the surface-code cost of a real RSA break, honest resource estimates with uncertainty bands, and Mosca's inequality turned into a migration-priority model. Grounded in the primary papers.
Why a quantum computer factors integers in polynomial time — the reduction to order-finding, the transform that reads a period, and where the difficulty really moved.
A quantum computer searches an unstructured space quadratically faster — which sounds alarming and is, in fact, the reason symmetric cryptography merely doubles its key sizes rather than dying.
Shor's circuit is short; running it is not. The gap between a proven algorithm and a working attack is entirely quantum error correction — and it can be quantified.
Quantum resource estimates span orders of magnitude and single-date predictions are unsound; this is how to read a claim, weight its assumptions, and turn a range into a decision.
A one-line inequality converts an uncertain quantum timeline into a decision you can make today — and shows that for long-lived secrets you are probably already late.