Overview

• The DRDO-Industry-Academia Centre of Excellence at IIT Delhi demonstrated free-space quantum secure communication over a distance exceeding one kilometre using an optical link.
• The experiment delivered a secure key rate of nearly 240 bits per second with a quantum bit error rate below 7%.
• By transmitting entangled photons through open air, the trial removed the need for disruptive fibre-optic infrastructure in challenging terrains and urban settings.
• Entanglement-based quantum key distribution detects any interception by disturbing the quantum state, providing inherently unbreakable encryption even if devices are compromised.
• Building on previous intercity and fiber-based QKD milestones, the breakthrough paves the way for long-distance quantum key distribution and the future quantum internet.