Quantum Breakthrough: Scientists At Raman Research Institute Achieve Key Milestone In Pursuit Of Secure Satellite-Based Communications

In October 2019  a sensational announcement by Google claimed that it had achieved ‘Quantum Breakthrough’ — it had  developed and harnessed  a quantum computer to solve a problem in seconds, that would have  taken conventional computers hundreds of years.

Ever since, there has been a global race among a handful of nations to harness quantum computing to further their own development goals. 

India embarked on its own national Quantum-enabled Science & Technology (QuEST) programme — and a key priority was the harnessing of Quantum technology for developing highly secure and encrypted communication systems. (What is Quantum Computing and Quantum communication? See primer at end of this article).

That mission  was brought a step closer to fruition last week, by a team of researchers at the Raman Research Institute (RRI) in Bengaluru. 

Founded in 1948 by the Indian physicist and Nobel Laureate, CV Raman, the institute since 1972 has functioned as an autonomous research institution of the Government of India’s Department of Science and Technology (DST).

Working in collaboration with the U.R. Rao Satellite Centre of the Indian Space Research Organisation (ISRO) also based in Bengaluru, a team at the Quantum Information and Computing (QuIC) Lab of the RRI has successfully demonstrated a secure channel of communication between  a stationary source and a moving platform. 

The significance of this breakthrough cannot be overstated:

Just over a year ago the same team demonstrated a similar  communication channel between two fixed locations on campus. 

By improving on this, to make one of the locations mobile, the researchers have now brought closer, their eventual mission of a secure quantum communication channel between a fixed station on earth and an orbiting satellite.

To maintain communication with a moving platform, the QuIC team developed a Pointing, Acquisition and Tracking (PAT) system, for the stationary source which must at all times remain in the Line of Sight of the moving platform.

What is unique to the RRI work is that it established a secure link between fixed and moving stations, using what is known as Quantum Key Distribution (QKD). This is the first time this has been achieved in India, says project leader, Urbasi Sinha.

She explains “To mimic satellite motion, we progressed from a home-built linear track to a circular track and then built an entire moving vehicle carefully aligned to the receiver”.

Why QKD? 

Classical cryptography — the coding and decoding of messages, as practiced today involves encrypting and sending a message and then decrypting it at the receiving end, using a combo of ‘public’ and ‘private’ keys. 

These keys depend for their strength on their length and the complicated math they are based on.

But with supercomputers becoming more powerful by the day — and more portable — public keys are increasingly breakable. This is where Quantum Keys are superior.

Quantum computing, unlike conventional digital computers, doesn't work with digital ones and zeroes. Quantum bits or Qubits as they are known, can be a one or a zero at the same time. That means with two Qubits you have four possible states.

The beauty of this, is that it is much more difficult for a hacker to tell if a particular bit is a one or a zero at any given time. 

In Quantum Key Distribution, encrypted data is sent in the old fashioned way, but the keys to  decrypt them are sent as Quantum bits. It makes the entire chunk of data much harder to hack or crack — and this is what the team at RRI has achieved, albeit over a fairly short distance.

QKD is currently the most secure means of facing any threats from efforts at breaking the algorithms of classical computing cryptography, adds Prof Sinha.

Think of it  this way (illustration above): In classical digital cryptography, when Alice communicates with Bob, there is the danger of Eve eavesdropping. 

Quantum communication using Quantum Key Distribution, makes the task of Eve, well nigh unachievable.

By establishing that India can harness the superior security of quantum cryptography and establish such secure links with mobile platforms, the researchers in Bengaluru, have brought nearer the day when such ultra secure links can be extended to satellite-based communication.

Quantum Primer

Quantum computing is a technology that harnesses the laws of quantum mechanics to solve problems so complex that classical supercomputers aren’t super enough to solve them. 

Quantum processors work with Qubits rather than bits to perform operations — and they can do this only at very low temperatures, close to absolute zero or minus 273 degrees Celsius.

Quantum Communications is a sub-field of quantum  physics, whose most useful application is the ability to send and receive information that is secure against eavesdroppers. It uses a process called Quantum Key Distribution or QKD.