India’s Progress in Quantum Communication

• India could become technologically capable of satellite-based quantum communication within the next 5 years, says Professor Bhaskar Kanseri of IIT-Delhi. • His team recently achieved quantum key distribution (QKD) over 1 km without using cables — the farthest such attempt in India.

What is Quantum?

Whether you know it or not, quantum physics touches our lives each day. Everything physical around us is made of matter, from the air we breathe to the water we drink—even our own bodies are made of matter. In its smallest measurable form, matter is made up of atoms. Within atoms are even smaller particles called electrons, protons, and neutrons—and protons and neutrons are made of even smaller units of matter called quarks.

Quantum physics is the study of these extremely small atomic particles and quarks. Quantum aims to understand the nature of energy and matter through these small particles in order to better understand the world around us and apply quantum theories to real-world technology solutions.

Applied quantum science is a foundational part of many components in many modern technologies, including cell phones and computers. In quantum computing, predictions are given in terms of probability, which allows us to find answers that traditional computers cannot provide.

What is Quantum Communication?

• It enables two parties to share “quantum keys” — secure codes made from photons (light particles). • Based on quantum mechanics, particularly quantum entanglement, where changes in one photon affect its pair instantly. • Any hacking attempt becomes immediately detectable, making it extremely secure.

Free-Space vs Cable Transmission

• QKD can be done through fibre optic cables or through “free-space” (without cables). • Cable-based QKD is stable but becomes expensive and less feasible over long distances. • Free-space QKD using satellites is ideal for long-distance communication.

Challenges in Free-Space QKD

• Atmospheric disturbances (pollution, turbulence, airflow) affect photon transmission, especially in urban areas like Delhi. • These lead to higher error rates compared to cable-based systems. • Better beam control and signal optimisation can help reduce errors.

Global Comparison

• China successfully demonstrated satellite-based QKD nearly 10 years ago due to early investment in the 2000s. • In 2017 and 2020, Chinese researchers exchanged quantum keys between satellites and ground stations 1,000–1,700 km apart.

India’s Current Status

• IIT-Delhi’s experiments are at proof-of-concept stage with a small team of 4–5 students.
• Moving forward will require well-funded, multidisciplinary teams and active start-up involvement.