Quantum Key Distribution: Secure Communication

TOPIC CLASSIFICATION

Subject: Science & Technology - Quantum Technologies - Secure Communication
Sub-topic: Quantum Key Distribution (QKD) - BB84 Protocol, E91 Protocol, Decoherence, Quantum Entanglement, No-Cloning Theorem, Heisenberg Uncertainty Principle, QKD vs Classical Cryptography, QKD Implementations (Fiber-based, Free-Space, Satellite-based), Micius Satellite (China), India's QKD Efforts - ISRO/RRI (300 km QKD), DRDO QKD, MeitY Quantum Communication Lab, National Quantum Mission (2023-2031)
Mains GS Paper-III: Science & Technology - developments in quantum technologies and their applications in security and communication.

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EXAMINER REASONING

QKD represents the frontier of secure communication - theoretically unbreakable encryption based on quantum mechanics. Prelims tests: BB84 protocol (Charles Bennett, Gilles Brassard - 1984), quantum bits (qubits), no-cloning theorem, Heisenberg uncertainty principle (measurement disturbs the system), photon polarisation, entanglement-based QKD (E91), decoy state protocol, Micius satellite (China), India's QKD milestones (300 km by ISRO/RRI, 100 km by DRDO). Mains demands: (a) why QKD is needed - Shor's algorithm breaks RSA-2048 encryption - quantum computers pose existential threat to classical cryptography - QKD provides information-theoretic security, (b) BB84 protocol - Alice sends photons in random polarisation bases - Bob measures in random bases - sifting - error correction - privacy amplification - eavesdropper detection (intercept-resend increases error...