Quantum Communication

Syllabus: GS3/Science and Technology

Context

• India has successfully demonstrated quantum secure communication using quantum entanglement over free space by the DRDO-Industry-Academia Centre of Excellence (DIA-CoE), IIT Delhi.
  • This marks a significant milestone in India’s quantum technology roadmap.

Key Highlights

• Technology Used: Quantum Entanglement-based Free-Space Quantum Key Distribution (QKD).
• Secure Key Rate: ~240 bits per second.
• Quantum Bit Error Rate (QBER): < 7%.
• Distance: Over 1 km free-space optical link on IIT Delhi campus.

Quantum Communication

• Quantum communication uses quantum physics, especially quantum entanglement, to create ultra-secure channels for sending information.
• Quantum Entanglement: When two photons are entangled, measuring one instantly determines the state of the other — even if they are far apart.
• Main purpose: To make communication leak-proof. Any eavesdropping attempt will disturb the entangled state, revealing the intrusion.

What is Quantum Key Distribution (QKD)?

• QKD allows secure exchange of encryption keys using quantum mechanics.
• Uses photons (light particles) as information carriers.
• Quantum entanglement-based QKD is highly secure — any hacking attempt disturbs the system and gets detected.
• Entanglement-based Quantum Key Distribution (QKD) Advantages:
  • Security even with imperfect or compromised devices.
  • Intrusion detection through quantum state disturbance.
  • More robust than traditional prepare-and-measure QKD methods.
• Applications:
  • Defence communications.
  • Secure banking and telecom networks.
  • Strategic sector data protection.
  • Cost-effective: Free-space QKD avoids costly fiber-laying in challenging geographies.

Why Free-Space Communication?

• Free-space or satellite-based QKD can connect long distances without laying cables.
• Cables (optical fiber) become costly and impractical over long distances.

Global Comparison

• China is leading with a 4,600 km quantum network since 2021.
  • China had demonstrated satellite-based quantum communication nearly one decade ago, as they had a head start in quantum communication activities since the early 2000s. 
• Since 2005, there have been ground demonstrations in Europe, Canada, and the United States of free-space (without cables) QKD greater than 100 km, suggesting that India still has much to cover regarding QKD-entanglement communication.

Challenges

• It requires not only adequate funds but also a large, dedicated team of multidisciplinary skilled experts for developing several types of enabling technologies. 
• Atmospheric disturbances increase error in free-space.
• India started late (2020s) and must catch up with global leaders.
• Using fibre optic cables provides a stable channel for quantum communication which free-space channels do not.

Future Plans

• Under the National Quantum Mission (NQM) India is focusing on satellite-based long-distance QKD.
• The support includes quantum start-ups, indigenous equipment, and lab-to-market technologies.
• India aims to achieve satellite-based QKD and a quantum network across India in 5–10 years.

Source: TH