Quantum Cryptography

Quantum cryptography's defining theoretical claim is that security can be grounded in physical law — a measurement disturbs a quantum state in a detectable way — rather than in the assumption that a given mathematical problem is hard to solve on any computer, including a future quantum one. Quantum key distribution is the technique within this field that has moved furthest from theory into commercial and government deployment; other quantum cryptographic primitives remain largely in research or early pilot stages.

The strategic driver behind quantum cryptography's current relevance is the long-term threat quantum computing poses to the asymmetric cryptography — RSA, elliptic curve Diffie-Hellman — that underpins most existing public key infrastructure: a sufficiently capable quantum computer could, in principle, break these algorithms, and adversaries capable of recording encrypted traffic today could decrypt it retroactively once such capability exists, a threat model commonly described as "harvest now, decrypt later." This creates real pressure on any organization protecting data with a long confidentiality shelf life to evaluate a transition path, whether toward quantum cryptography's physical-layer approach or toward post-quantum cryptography's algorithmic approach — the two are complementary responses to the same threat, not competing solutions, since quantum cryptography secures key exchange while post-quantum algorithms can secure the broader cryptographic stack including digital signatures, which quantum key distribution does not address at all. For CE verticals holding long-lifetime sensitive data — government and defense communications, and critical energy or industrial control system configurations that will remain sensitive for decades — this transition planning is a near-term compliance and risk consideration even though large-scale cryptographically relevant quantum computers do not yet exist.