India, Sept. 12 -- By almost any measure, India has built one of the most sophisticated digital economies in the world and done so faster than almost anyone anticipated. That infrastructure runs on cryptography. Digital certificates, encryption protocols, and cryptographic keys are what make Unified Payments Interface (UPI) transactions trustworthy, what authenticate users across government services, and what secure the data flowing through India's technology and financial sectors. Most of this infrastructure is invisible until it fails or until the assumptions it was built on no longer hold.

Quantum computing is approaching the point where some of those assumptions will be tested. Preparing for a quantum-secure future, therefore, cannot...