No publicly known quantum computer currently has the number of stable, error-corrected qubits required to run Shor's algorithm against the key sizes used in cryptocurrency. Current estimates from quantum computing researchers suggest a cryptographically relevant quantum computer capable of breaking elliptic curve cryptography would require millions of physical qubits with very low error rates, a capability that leading quantum hardware teams have not yet demonstrated and that most researchers place at least a decade away under current trajectories. However, the timeline has significant uncertainty in both directions, and the standard security recommendation is to begin migrating to quantum-resistant cryptography now rather than waiting until the threat is imminent, because the migration process for global blockchain infrastructure will take years and cannot be completed quickly once a credible threat emerges.