In a major step forward towards satellite-based quantum communication, scientists from Ahmedabad-based Space Applications Centre and Physical Research Laboratory successfully demonstrated quantum entanglement. Using real-time Quantum Key Distribution (QKD), they conducted hack-proof communication between two places separated by 300 meters.

Quantum communication is one of the safest ways of connecting two places with high levels of code and quantum cryptography that cannot be decrypted or broken by an external entity. If a hacker tries to crack the message in quantum communication, it changes its form in such a manner that would alert the sender and would cause the message to be altered or deleted.

During the demonstration, scientists managed to create an atmospheric channel on the ground to enable sharing of quantum-secure text, image transmission and quantum-assisted two-way video calling. The experiment was conducted between two buildings separated by 300 meters at the Space Applications Centre.

"This experiment and demonstration were repeated over several nights to ensure the repeatability and robustness of an indigenously developed QKD system capable of seamlessly generating and utilizing secure keys for various applications," ISRO said in a statement, adding that this is yet another significant step towards the development of the planned Satellite-Based Quantum Communication.

The demo was conducted at SAC, Ahmedabad, between 2 buildings separated by a distance of 300m

ISRO chief S Somnath was present to witness the demonstration during which various images were encrypted using a generated quantum key and transmitted over a classical channel from one building to another building. They were then decrypted at the receiving terminal in real-time.

ISRO said that to achieve the feat, scientists developed various key technologies like robust & high brightness entangled photon source (EPS), BBM92 protocol implementation, NavIC enabled synchronization, polarization compensation techniques, among others. A cryptographic application software suite with integrated quantum security has also been developed and demonstrated for text, image, video encryption/decryption.

" The Department of Space is getting ready for satellite-based demonstrations of fundamental quantum mechanics experiments as well as quantum communication for future-proof data security," ISRO said.

The latest breakthrough comes on the back of an earlier demonstration of quantum secure video-conferencing in free space, over a distance of 300 meters in March last year. Former ISRO chief K Sivan had said that the space agency was working on a hackproof communication system. He had said that ISRO's work will make the relay faster and much more secure in the coming era of quantum computers that explore quantum mechanics.

China already has a satellite dedicated to quantum information science, Micius, and demonstrated quantum communication in a laboratory over a coiled optical fibre up to 404 kilometres long.