Department of Space Demonstrates Entanglement Based Quantum Communication Over 300m Free Space Along with Real Time Cryptographic Applications

AHMEDABAD, India (ISRO PR) — On 27 January 2022, scientists from the two premier laboratories of Department of Space (DOS), viz. Space Applications Centre (SAC) and Physical Research Laboratory (PRL), both from the city of Ahmedabad, have jointly demonstrated quantum entanglement based real time Quantum Key Distribution (QKD) over 300m atmospheric channel along with quantum-secure text, image transmission and quantum-assisted two-way video calling.

The demonstration was conducted at SAC, Ahmedabad, between two buildings separated by a distance of 300 m. This experiment and demonstration were repeated over several nights to ensure the repeatability and robustness of indigenously developed QKD system capable of seamlessly generating and utilizing secure keys for various applications.  

Shri. S. Somanath, Chairman, ISRO / Secretary, DOS has witnessed this live breakthrough demonstration at SAC, Ahmedabad.  Shri. Nilesh M Desai, Director SAC and Dr. Anil Bhardwaj, Director PRL were also present during the demonstration. Various images were encrypted using generated quantum key and transmitted over classical channel from one building to another building separated by 300m and decrypted at the receiving terminal in real time.

This is yet another significant step towards the development of the planned Satellite Based Quantum Communication (SBQC). This feat comes after the earlier breakthrough demonstration of quantum secure videoconferencing by SAC-ISRO using ‘prepare-and-measure’ quantum communication technology, in free space, over a distance of 300 m on 19 March 2021.

In order to achieve this technology feat, scientists developed various key technologies like robust & high brightness entangled photon source (EPS), BBM92 protocol implementation, NavIC enabled synchronization, polarization compensation technique etc. A cryptographic application software suite with integrated quantum security has also been developed and demonstrated for text, image, video encryption/decryption.

The BBM92 protocol based quantum communication link was demonstrated in the experiment. The secure-key-rate achieved was ~1.8 kbps, with Quantum Bit Error Rate (QBER) of less than 10%. Quantum entanglement was achieved with Bell’s parameter and quantum visibility greater than 2.2 and 80% respectively.

With these developments, ISRO, 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.