How this site is made

Plain Quantum explains quantum computing and post-quantum cryptography for people who need to understand them without becoming physicists or cryptographers. This page sets out how the material is put together: where facts come from, what's illustrative, what hasn't been tested, and how mistakes are corrected.

Sources

• Public sources only. Everything is built from published standards, government and regulator documents, peer-reviewed research, reports of experiments and companies' own announcements. Nothing comes from any employer's or client's internal information.
• Primary sources first. Figures and dates are checked against the original document wherever it can be reached. Where only secondary reporting is available, it's tagged as a reference rather than presented as the original.
• Tagged by kind. Each source list labels its entries: standard, government guidance, industry guidance, peer-reviewed paper, preprint, experiment, company announcement, book, course or reference. A preprint hasn't been peer-reviewed; an experiment shows what was demonstrated, not what is ready for production.

Dates and their status

Dates in this field are easy to overstate, so the site tries to say what kind of date each one is:

• Final standard: published and in force, such as FIPS 203, 204 and 205.
• Draft guidance: proposed and open to change, such as NIST IR 8547's 2030 and 2035 dates.
• Government milestone: binds government systems only, such as Canada's federal roadmap.
• Regulator or sector guidance: describes good practice, sometimes without dates, such as OSFI's 2026 bulletin or the G7 roadmaps.
• Planning horizon: a date that guidance commonly points to, such as 2035, which isn't a deadline set for banks.

There are no predictions of when a quantum computer will break today's encryption. Published resource estimates are reported as estimates under their authors' assumptions.

What's illustrative

• Larkfield Bank is fictional. The banking guide follows an invented mid-sized bank so that the steps have something concrete to apply to. Its systems, suppliers, numbers and scores are illustrative, built from how banks and payment systems are publicly described as working, not from any real institution.
• The payment-flow CBOM is a reference model. The illustrative inventory of a wire-payment flow describes a representative estate. Each entry is labelled documented, where the cryptography is described in public material for that platform, or inferred, where it's a reasonable assumption that isn't publicly confirmed.
• Simplifications are flagged. Analogies are labelled as analogies, and the aim is that a reader moving on to a technical source finds nothing here was wrong.

What hasn't been validated

• The self-assessment's scoring and bands haven't been benchmarked against real banks. It gives an indicative profile, not a maturity rating.
• The templates and the prioritisation weights haven't been tested in a real institution's programme. They're starting points to adapt.
• The Mosca calculator is a planning heuristic. It covers confidentiality, not signatures, and it can't say how likely a quantum computer is within any period.

If you use any of these in practice and find where they fall short, that feedback is welcome.

Reviews and updates

Every page shows when it was last reviewed. Pages that track fast-moving documents, such as Post-quantum in Canada and the guide's regulatory map, are rechecked when the underlying documents change. Your calculator inputs and self-assessment answers stay in your browser; the site uses cookie-free page-view analytics only.

Corrections log

Material corrections and clarifications to published pages are listed here, newest first. The log starts on 12 October 2026. Spotted an error? Email hello@plainquantum.com.

• 12 October 2026, banking guide chapters 1 to 3, the inventory template and the Q-day quick answer. Renamed the quantum status labels from "broken, weakened, fine" to "vulnerable, check key size, not affected", and defined them in chapter 1, so they no longer imply anything is broken today.
• 12 October 2026, Banking guide chapter 1. Clarified that working out a private key from a public key needs a sufficiently capable quantum computer, and applies to RSA and elliptic-curve cryptography.
• 12 October 2026, Why your bank is already preparing; Banking guide chapter 7. Clarified that the commonly cited 2030 and 2035 dates come from government roadmaps and draft guidance, not deadlines set for banks.
• 12 October 2026, four quick answers. On phones, the comparison tables on the ML-KEM, CRQC, logical qubit and QKD pages briefly showed column labels shifted by one. Fixed the same day.
• 12 October 2026, companion CBOM project. Project Leap figures were corrected to match the BIS report, an unverified SWIFT date was removed, and the project page now states up front that it's an illustrative reference model.