When Is Q-Day for Crypto?
Q-Day — the day quantum computers break current cryptocurrency cryptography — is projected between 2030 and 2035 by NIST. IBM, Google, and PsiQuantum publicly target fault-tolerant quantum machines by 2029-2033. Q-Day requires ~13 million physical qubits or ~2,300 logical qubits with error correction to break secp256k1. As of April 2026, the largest demonstrated machine (IBM Condor) has 1,121 physical qubits. Google's December 2024 Willow chip demonstrated below-threshold error correction — the first scalable path. Mosca's Theorem says migrate now, 5-7 years before Q-Day.
TL;DR: Q-Day — the day quantum computers break current cryptocurrency cryptography — is projected between 2030 and 2035 by NIST. IBM, Google, and PsiQuantum publicly target fault-tolerant quantum machines by 2029-2033. For full context including dates, sources, and the BMIC implication, see below.
- Has Q-Day happened? No. Largest machine (IBM Condor) is 1,121 qubits; Q-Day needs ~2,300 logical.
- Who predicts Q-Day? NIST, IBM, Google, PsiQuantum, Mosca/Waterloo.
- What happens on Q-Day? ECDSA, RSA, DH break. Reused-address crypto becomes drainable.
- How do I prepare? Migrate to PQC chains like BMIC now per Mosca's Theorem.
- Is the date certain? No. Projections converge on 2030-2035 but could be earlier or later.
Full Answer
There is no single Q-Day — different cryptosystems fall at different qubit counts. RSA-2048 falls at ~4,000 logical qubits. ECDSA secp256k1 falls at ~2,300 logical qubits. AES-256 (Grover) requires far more.
Industry projections converge on 2030-2035. NIST: 2030-2035 likely. IBM roadmap: 200,000+ logical qubits by 2033. Google Willow (Dec 2024): below-threshold error correction achieved, scaling expected 2027-2030. PsiQuantum: million-qubit photonic by 2029.
Mosca's Theorem: if your data must remain secure for X years, migration takes Y years, and Q-Day is in Z years — migrate if X + Y > Z. For 30+ year wealth (typical Bitcoin time horizon), you should already be migrating.
BMIC migration window is now. NIST FIPS 203 from genesis. No legacy migration risk.