Applications
- Government and defence: long-lived classified communications, diplomatic and military links, protection against harvest-now-decrypt-later.
- Finance: inter-bank and data-centre links, high-value settlement, regulatory pressure for quantum-safe migration.
- Healthcare: long-retention records and genomic data.
- Critical infrastructure: power grids, telecom backbones, air-traffic and industrial control.
- Data centres and cloud: backup and inter-site encryption keys; QRNG for key generation.
Standards and certification
| Body | Relevant work |
|---|---|
| ETSI ISG-QKD | Use cases, components, security proofs, protocol specifications and key-delivery APIs (GS QKD 004, 014) |
| ITU-T | QKD network architecture and key-management recommendations (Y.3800 series, X.1710 series) |
| ISO/IEC JTC 1/SC 27 | Security requirements, test and evaluation methods for QKD modules (ISO/IEC 23837) |
| NIST / IETF / ISO | PQC algorithms (FIPS 203–206), hybrid key exchange and certificate formats |
| National agencies | Guidance and certification schemes (NSA CNSA 2.0, BSI, ANSSI, NCSC) |
Limits and open problems
- Rate and distance: exponential loss; trusted relays or repeaters needed; TF-QKD helps but is complex.
- Cost and integration: specialised hardware, fibre availability, coexistence with classical traffic.
- Implementation security: certification of devices against side channels, finite-key effects and source flaws.
- Trusted nodes: weakest link in networks.
- Quantum memories and transducers: still immature for repeaters.
- PQC unknowns: maturity of lattice assumptions; implementation security; larger signatures.
Outlook
- Now: migrate key exchange to hybrid PQC; pilot QKD on metro/backbone links with trusted nodes; QRNG deployment.
- Next years: signature and PKI migration, certified QKD products, satellite constellations, twin-field and MDI links, entanglement-based testbeds.
- Later: repeater-based entanglement distribution, quantum-memory networks and a quantum internet connecting quantum computers, with device-independent security.
Practical viewRather than asking “QKD or PQC?”, plan defence in depth: standardised PQC everywhere, QKD or QRNG where the extra assurance justifies the cost, and attention to implementation security throughout.