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In an era where quantum computers will break traditional encryption, organisations face an unprecedented cybersecurity challenge. The solution is Quantum Key Distribution (QKD) – the only encryption method that uses the laws of quantum physics to guarantee unconditional security. This informative and comprehensive blog explores everything you need to know about QKD, from fundamental principles to real-world deployments.
Quantum Key Distribution (QKD) is a radical cryptographic technique that leverages the principles of quantum mechanics to generate and distribute encryption keys with absolute security. Unlike traditional encryption methods that rely on mathematical complexity, QKD's security is guaranteed by the fundamental laws of physics or photonics.
At its core, QKD uses quantum properties of photons (light particles, which are a phenomenon of nature) to generate symmetric encryption keys simultaneously at both ends of a communication channel without ever transmitting the key itself.
The game-changing feature? Any attempt to interrupt or measure these quantum states inevitably disturbs them, immediately alerting both parties to the presence of an eavesdropper/ adversaries.
The Quantum Threat is Real. According to the Hudson Institute, a quantum attack could result in over $3 trillion in damage to the US economy alone. Quantum computers, when sufficiently powerful, will break RSA, ECC (expected in 2026 or by 2028-2030), and other public-key cryptosystems that secure today's digital infrastructure.
Adversaries are already engaging in "harvest now, decrypt later" attacks – collecting encrypted data today to decrypt once quantum computers become available. QKD provides the answer: Future-proof encryption that remains secure even against quantum computer attacks. It's not just quantum-resistant – it's quantum-proof.
QKD operates on two fundamental quantum principles:
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DV-QKD encodes information in discrete quantum states of single photons, such as polarisation or phase. It uses single-photon detectors, has proven technology with extensive real-world deployments, and achieves a range up to 150-200 km point-to-point. Best for high-security applications in defence, government, and critical infrastructure.
CV-QKD encodes information in continuous properties of electromagnetic fields using coherent light states. It uses standard telecom components, offers higher key generation rates at shorter distances (50-80 km), and is more cost-effective. Best for last-mile connectivity, data centre interconnections, and enterprise deployments.
QNu Labs embodies India's Atmanirbhar Bharat (Self-Reliant India) vision with completely indigenous quantum security technology. Designed, developed, manufactured, and certified entirely in India. Founded in 2016 at the IIT Madras Research Park. Supported by India's National Quantum Mission. Positioning India as a global quantum technology powerhouse with complete technology sovereignty.
11 granted patents (including 3 US patents) with 15 patents pending globally. Patents cover QKD hardware, QRNG technology, hybrid security architectures, and quantum network topologies. This is India's largest quantum security IP portfolio.
While competitors globally achieve 80-100 KM spacing between QKD nodes, QNu's Armos™ QKD system delivers 150-200 KM point-to-point range – nearly double the industry standard. This breakthrough means a 60% infrastructure reduction for long-distance networks. Example: A 500 KM network requires only 4 nodes (QNu) vs 10 nodes (global standard).
Armos™ QKD System: Production-ready DV-QKD hardware with 150-200 km range, multiple network topologies (point-to-point, trusted node, hub & spoke), and seamless integration.
QNu’s Tropos™ QRNG (Quantum Random Number Generator) provides true quantum randomness, the foundation of all cryptography and integrates with QKD – where keys are generated from this true quantum randomness.
ChaQra Architecture: Hub-and-spoke configuration detailed in Nature's Scientific Reports (July 2024), enabling scalable quantum networks with SDN switching.
In November 2025, QNu Labs successfully demonstrated India's first and one of the world's most extensive QKD networks spanning over 500 Kilometres, which was announced at ESTIC 2025 by the Hon’ble Union Minister of India, the Principal Scientific Adviser to the PM’s Office, DST, and many other dignitaries. This has been deployed over existing optical fibre infrastructure with 60% infrastructure efficiency compared to global standards.
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