Why in News?

Recently, the Ministry of Defence announced that IIT-Delhi and DRDO scientists successfully demonstrated quantum communication over a distance of more than 1 km in free space, marking a major breakthrough in quantum cybersecurity.

What’s in Today’s Article?

• Understanding Quantum Communication
• Working of Quantum Key Distribution (QKD)
• IIT-Delhi’s Quantum Communication Achievement
• What Lies Ahead for Quantum Communication in India

Understanding Quantum Communication

• About Quantum Communication
  • It uses principles of quantum physics—especially quantum entanglement—to create highly secure communication channels.
  • It ensures that any attempt to intercept the communication is immediately detected.
• The Role of Quantum Entanglement
  • Quantum entanglement is a phenomenon where two particles become so closely linked that a change in one instantly affects the other, regardless of the distance between them.
  • When two photons are entangled, measuring one instantly determines the state of the other, regardless of distance.
  • This makes quantum communication highly resistant to eavesdropping.
• Applications in Defence
  • Due to its leak-proof nature, quantum communication is especially valuable in military and national security settings.
• Key Method: Quantum Key Distribution (QKD)
  • QKD is a major technique within quantum communication that enables two parties to share encryption keys securely, with any interception attempts being detectable.

Working of Quantum Key Distribution (QKD)

• Purpose of QKD
  • QKD enables two parties to securely share a secret encryption key.
  • This key is later used to encrypt and decrypt messages using traditional algorithms (e.g. AES).
• QKD Is Not Encryption
  • QKD does not encrypt the message itself.
  • It only ensures that both parties receive an identical key in a way that cannot be intercepted without detection.
  • Just like a letterbox is publicly known but accessible only with a private key, QKD ensures that while the communication channel is known, the key remains private and secure between the sender and receiver.
• Types of QKD
  • Prepare-and-Measure QKD
    • One person prepares photons in specific quantum states and sends them to another, who measures them to establish a key.
  • Entanglement-Based QKD
    • A source produces entangled photon pairs—one sent to the first person, the other to the second person.
    • The correlated measurements help them derive the same key securely.
• Security Advantage
  • Any attempt to intercept the photons in transit disturbs their quantum state, immediately alerting the parties and ensuring tamper detection.

IIT-Delhi’s Quantum Communication Achievement

• Latest Breakthrough: 1 km Free-Space QKD
  • The IIT-Delhi team successfully demonstrated entanglement-based Quantum Key Distribution (QKD) over 1 km through open air on the IIT campus.
  • This marks progress beyond fibre-based transmission.
    • The photons travel through open air, not through cables or fibres.
    • This is useful for communicating over long distances, even between buildings or from the ground to satellites.
• Towards Satellite-Based QKD
• The experiment aims to lay the groundwork for ground-to-satellite QKD, where satellites could beam encryption keys securely to any location across India via atmospheric transmission.
• Performance Metrics
  • Secure key rate: ~240 bits per second
  • Quantum bit error rate (QBER): Less than 7%
  • This low error rate is acceptable and shows the system’s viability despite challenges like air turbulence, detector noise, and ambient light.
• How It Works
  • Entangled photons were sent to two receivers.
  • When both receivers measured their respective photons, results matched over 93% of the time—validating entanglement and secure key distribution.
• Past Milestones by IIT-Delhi Team
  • 2022: Quantum link between Vindhyachal and Prayagraj
  • 2023: 380 km QKD using telecom fibre (Quantum Bit Error Rate (QBER): 1.48%)
  • 2024: QKD over 100+ km optical fibre link
  • These progressive steps showcase India’s growing capability in quantum-secure communication infrastructure.

What Lies Ahead for Quantum Communication in India

• Building a Quantum Communication Network
  • The next step is to establish a multi-node quantum network, enabling secure communication across various locations.
  • India aims to join global leaders like China, which already has a 4,600 km hybrid quantum network combining satellite and optical links.
• Civilian Applications
  • Quantum communication also holds promise for banking, telecom, and data security—where ultra-secure channels are vital to protect sensitive information.
• Towards a Quantum Internet
  • A future quantum internet could revolutionise:
    • Distributed quantum computing
    • Precision sensing
    • Secure time synchronisation
    • Highly encrypted communication networks
  • The U.S. is targeting such a network by the mid-2030s.
• Government Support: National Quantum Mission
  • To accelerate progress, the Indian government launched the National Quantum Mission in 2023, allocating Rs 6,000 crore for the 2023–2031 period to support research and infrastructure development in quantum technologies.