In a landmark achievement, scientists at IIT-Delhi and Defence Research and Development Organisation (DRDO) demonstrated quantum communication over a distance of more than 1 km via a Free Space Optical (FSO) link. Why is this milestone so important to India? I write this article on the popular demand of our readers to explain the significance of this achievement in simple language that can be easily understood by them. Let us start with a little background.
We are slowly moving from classical modern-day computers and supercomputers to quantum computers that use core concepts of quantum mechanics to (i) solve very complex problems at much higher speed than our classical computers, and ii) Ensure safe and secure data transmission at superfast speed. Very soon, quantum technology will pose the greatest cyber threat to our personal as well as the government’s military and intelligence data. To counter this risk, India needs to speed up research in quantum technology and develop quantum-safe encryption and secure quantum communication protocols that are crucial to ensure data security in the coming years.
Classical Computers today use Binary code to process and store our information into a sequential data format that relies on 0 and 1, called bits. These bits are translated into electric current flows, 0 when there is no flow and 1 if the current flows. The information could be anything from our tweets, emails, iTunes, YouTube videos, digital transactions or any other sensitive data. To ensure safety against cyberattacks and maintain confidentiality and integrity of this information Ron Rivest, Adi Shamir, and Leonard Adleman (RSA) developed a mathematical algorithm to encrypt this data into an unreadable coded format that has embedded software keys needed to decrypt the code. This is the most popular algorithm in use today.
RSA algorithm uses unique properties of prime numbers to secure online transactions. Prime numbers are integers greater than 1 and are only divisible by 1 and themselves. In this algorithm, two enormous prime numbers are multiplied, and the product is published as a part of the encryption key needed to generate the decryption key. For example, take a number, say N=15, that is a product of two prime numbers, 3×5=15; this is easy. Make it harder by taking a larger number, say N=694921, which is a product of two prime numbers, 787×883. Now take a very large number, say N=188,538,889,076,768,372,354,881,165,818,173,073,829, and try to figure out its prime factors. It is extremely difficult because this number is a combination of two 64-bit primes, with 20 digits each. A 64-bit number ranges from 0 to 18,446,744,073,709,551,616 and has a vast number of prime numbers in between. This is exactly the idea behind RSA algorithm to have a very large encryption key that cannot be decoded.
Quantum Computers will change the way computations are done, which would easily decode algorithms like RSA. Before proceeding further, let us understand what exactly quantum is. We all studied that an atom is the smallest unit of matter, be it is solid, liquid, or gas. A quantum (plural: quanta) is the smallest discrete unit of any physical quantity involved in an interaction at the subatomic level. For example, a quantum of light is a photon, or a quantum of electricity is an electron. Quantum computing uses two core concepts of Quantum mechanics, that is, quantum superposition and quantum entanglement. Quantum superposition means that a quantum exists in multiple states simultaneously. For example, when you toss a coin in the air, both head and tail possibilities exist when the coin is spinning in air but will result in either a head or a tail when it lands on the ground. Another example could be light that exhibits wave-particle duality. When light is viewed as a wave, phenomena like diffraction and interference can be explained and when viewed as particles (photons), the photoelectric effect can be explained. Quantum entanglement is a phenomenon where two or more quanta become linked together in a way that their fates are intertwined, regardless of the distance separating them. So, if you measure a property of one entangled particle, you instantly know the corresponding property of the other, even if they are light-years apart. Albert Einstein called this strange phenomenon as spooky action at a distance.
Comparison of Classical with Quantum computers: As described earlier, our classical computers use binary code, where the smallest piece of information is stored as bits that take the value of either 0 or 1. So, 1 bit will have only 2 possible values, 2 will have 4 (2×2), 3 will have 6 (3×2), 4 will have 8 (4×2), and so on. This means that bits take values that are multiples of 2. In contrast, bits are called qubits (quantum bits) in quantum computing. Because of the quantum superposition property, each qubit takes both 0 and 1 values. So, 1 qubit will have 2 values (1×2), 2 will have 4 (2×2), 3 will have 8 (2x2x2), 4 will have 16 (2x2x2x2), 5 will have 32 (2x2x2x2x2), and so on. In short, while bits take values which are multiples of 2, qubits take values which are powers of 2, making the process insanely fast. So, to break into a 64-bit encryption key, a modern supercomputer may take decades, but the same can be done in minutes with Quantum computers. That is the real threat, and we need to secure our data by developing quantum keys using quantum technology.
Quantum communication: The other important aspect is Quantum communication using the entanglement property for secure data transmission, with Quantum Key Distribution (QKD) being a prominent example. What IIT-DRDO scientists achieved is entanglement-assisted quantum secure communication for 1 km via a Free-Space Optical (FSO) link using a laser beam in air without relying on optical fiber cables. As the name implies, both laser and optical fiber cables use light to transmit data. Earlier, DRDO had successfully demonstrated India’s first intercity quantum communication link between Vindhyachal and Prayagraj in 2022, using commercial-grade underground dark optical fiber cables and followed it up with the successful distribution of quantum keys using entanglement over a 100 km spool of telecom-grade optical fiber cable in 2024. This is the first time that the FSO link has been used for QKD communication for 1 km, which will be enhanced in the future. In laser communications infrared light band of the Electromagnetic (EM) spectrum, which consists of particles and waves throughout space, is used. The infrared band packs more data into significantly tighter light waves with higher frequencies, unlike the radio waves band of lower frequencies, meaning ground stations can receive more data at once, making the communication much faster. The laser-based communication is most secured because information is encoded into individual light particles called photons, and the laws of physics do not permit this information to be extracted or copied, as the very act of measuring a quantum system changes its state.
The race for quantum technology is now heating up with tech giant IBM and Google leading the race along with research in universities in the USA, UK, Australia, China, Singapore, Austria, and Germany. Google reported a 20-fold reduction in computing resources required to break algorithms like RSA. Chinese scientists broke RSA encryption when they factored a 22-bit integer using a quantum annealing processor. Similarly, Canadian startup Nord Quantique announced a breakthrough with a quantum computer that consumes 2,000 times less power than a supercomputer and solve problems 200 times faster.
Thanks to the initiatives of the Modi government in the last decade, India, too, is at the forefront of quantum technology research. In 2021, IIT-Roorkee, IISc Bangalore, and C-DAC joined hands to indigenously develop the country’s first Quantum Computer Simulator toolkit. Not to lag behind the Military College of Telecommunication Engineering (MCTE), Mhow developed indigenous post-quantum cryptography applications to enhance capabilities across various domains. Two weeks back, a report in The Economic Times, post Sindoor operation, quoted a tweet of the Indian Army on X with a caption “Enabling the Battlefield of Tomorrow with Quantum Tech”. This is very heartening. Now, with this latest achievement of the IIT-DRDO joint venture, India may surprise the world with its innovative powers that were underutilised for want of challenges. With a ₹6003.65 crore budget outlay for the National Quantum Mission for 2023-24 to 2030-31, India is on the right path to establish itself as a serious contender in the race towards the quantum pole position.
I conclude my article with a thought that the technology race resembles very much like episodes of Tom and Jerry cartoons, where there is a never-ending chase for stealing a piece of cheese. So, my guess is we need to keep fortifying our systems, be a step ahead of cyber thieves and hackers, and keep our fingers crossed while hoping for the best.
