Quantum Computing Fundamentals

Quantum computing represents a fundamentally different model of computation. Where classical computers process information as bits (0 or 1), quantum computers use qubits that can exist in superposition — simultaneously representing both states. Combined with entanglement and quantum interference, this enables certain algorithms to solve problems exponentially faster than any classical machine.

The cryptographic impact is profound. Shor's algorithm, running on a sufficiently powerful quantum computer, can factor large integers and compute discrete logarithms in polynomial time — breaking RSA, ECC, and Diffie-Hellman, the public-key cryptosystems that underpin virtually all secure communications on the internet today. Grover's algorithm effectively halves the security of symmetric ciphers, meaning AES-128 would offer only 64-bit security against a quantum adversary.

While fault-tolerant quantum computers capable of running Shor's algorithm at scale do not yet exist, progress is accelerating. IBM, Google, Quantinuum, and others are steadily increasing qubit counts and reducing error rates. The security community broadly agrees that organizations should begin preparing now — not because the threat is imminent, but because cryptographic migrations take years and sensitive data intercepted today could be decrypted in the future.