The whole world is in a race to build quantum computers – computers that have the potential to be so powerful that they would make today’s fastest supercomputers look totally pedestrian. But what is a quantum computer?
Quantum physics describes the behavior of atomic and subatomic fundamental particles such as electrons and photons and has given rise to a set of powerful mathematical rules and ideas that explain the world of very small. It is a world built on probability and chance, where particles can also behave like waves. A quantum computer operates by controlling the behavior of these particles. It is a new kind of device which can harness the principles of quantum mechanics to deliver huge leaps forward in processing power and outstrip even the most capable of today’s, and even tomorrow’s, supercomputers.

2. Regular computer functions on the basis of a bit, a binary digit, which can switch between the two states of 0 or 1 (off or on, false or true, low or high). A
quantum computer is different. A quantum bit, or a qubit, which represents a subatomic particle such as an electron or a photon, has a more fluid non-binary identity. It can switch between 0 and 1 and also take numerous possible combinations of 0 and 1, all at the same time. This ability of qubit to be in multiple states at the same time is called superposition. If the two states of a bit, 0 and 1, can be thought of as the north and south poles of a sphere, the qubit, when in superposition, can be anywhere on the sphere. We can’t locate it exactly but scientists can manipulate it to perform operations. A quantum computer with several qubits in superposition can crunch through a vast number of potential outcomes simultaneously and that is the secret of its power. It can manipulate qubits and harness the superposition to have applications of far reaching
consequences.

3. This ability of the quantum computers, to perform large number of calculations simultaneously and thereby power exciting advances in various fields, is due to the unique characteristics of atomic and subatomic particles, which is their quantum states and which, in turn, correspond to the state of qubits. Quantum states, however, are incredibly fragile and easily destroyed by temperature and pressure fluctuations, stray electromagnetic field and collision with nearby particles. This is due to a phenomenon called de-coherence, which means interaction of qubits with their environment can cause their quantum behavior to decay, tumble out of superposition even before the job is done, and ultimately disappear. This is why quantum computers need elaborate arrangements to protect them from any outside interference, by placing them in super-cooled
fridges or vacuum chambers. And, this is the reason why, for now, the powers of quantum computers have largely remained theoretical. We are still a few years away from getting quantum computers that will be broadly useful.

4. Quantum computers, though still a work in progress, promises to provide several path breaking applications in our day to day life and industry. First of all, quantum uncertainty could be used in improving our encryption technology. The system we use to protect our data today is increasingly becoming vulnerable
because of advances in technology. Adding to the concern is the advent of quantum computers which, with its enormous computational powers, would have the potential to easily crack most of the encryptions we use today. The solution lies in pitting quantum versus quantum, i.e. by utilizing quantum effect itself to
make encryptions stronger. Random numbers generated by a programmed software or a mathematical recipe are not truly random. They will have some subtle pattern to them which will make them predictable and, consequently,vulnerable to analysis. But the quantum world is truly random. So, it makes sense
to take advantage of this intrinsic randomness. Quantum uncertainty could be used to create keys or codes for encrypting messages. Quantum data generators can produce an endless stream of random numbers at high speed.

5. Secondly, the transmission of encrypted messages is complete only when the codes have been safely delivered to the intended recipient. This can be ensured by using quantum key distribution, which leverages a fundamental characteristic of quantum physics where light sometimes behaves as waves (electro-magnetic
radiation) and sometimes as particles or photons. An object becomes visible when light waves are reflected from its surface, or if the object is very small, like sub-atomic particles, when the photon interacts with it. The very act of looking at aquantum particle, therefore, howsoever surreptitiously done, would change its
state as the photons would have interacted with it. So, if a third party tries to intercept the codes to copy, sent as quantum effects even over a laser beam, he would leave tell-tale signs of having interfered with the state of the quantum particles, which could be detected at the other end and discarded.

6. Thirdly, quantum technologies could transform health care and medicine.Quantum biology is an emerging area of science that is growing very rapidly. The living cells and its constituents are very small. If the subject of study gets smaller and smaller, down to the atomic and sub-atomic size, quantum principles will
come into play. Quantum mechanics underpins organic chemistry as it gives us the rules that tell us how the atoms fit together to make organic molecules. Organic chemistry, scaled up in complexities, gives us molecular biology which leads us to life itself. In fact, there are certain phenomena in biology that can be
adequately explained by quantum principles, such as quantum tunneling, quantum coherence and quantum entanglement. Quantum tunneling explains the role enzymes play while quantum coherence explains the impact of photosynthesis. Quantum entanglement, in all likelihood, helps the famed migratory cranes and other birds to navigate, from northern Asia over the Himalayas to the Indian subcontinent to escape harsh winters, with the help of earth’s magnetic field.

7. Fourthly, the process of successful drug designing involves the identification of particular molecules, synthesis and test of chemical compounds for their pharmaceutical efficacy. Computer-Aided Drug Design (CADD) is a specialized sub-discipline of drug designing that uses computational methods to investigate and
predict drug-receptor interactions. Quantum mechanics is an essential tool in CADD research. The identification of molecules for drug development is a challenge because correctly calculating the quantum properties of all atoms in a molecule is a difficult task even for a supercomputer. But a quantum computer
can do it easily because it operates using the same quantum properties as the molecule it is trying to simulate. Future large scale quantum simulations for drug development could perhaps lead to treatment of even diseases like the Alzheimer’s. 

8. Fifthly, Scientists have generated pairs of qubits that are ‘entangled’, which means the two members of a pair existing in a single quantum state. Changing the state of one of the qubits will instantaneously change the state of the other in a predictable way. This happens even if they are separated by long distances.
Nobody really knows quite how or why entanglement works. It even baffled Einstein, who famously described it as ‘spooky action at a distance’. Entanglement can be used for transmission of quantum information from one location to another. It has already been demonstrated in laboratories. The process is called teleportation. The Chinese scientists have claimed (July 2017) to have successfully transmitted the quantum state of a photon from an earth station to a satellite, 500 to 1,400 kilometers away, in a low earth orbit. Recently, the Austrian and Chinese scientists succeeded (August 2019) in teleporting a piece of quantum information based on all three states (i.e. 0, 1 and superposition), or a qutrit, for the first time. This possibly suggests that in future we could have quantum networks that would be able to carry much more data and we might also be able to create unhackable quantum internet protected by the fundamental laws of physics as any interference would break up the information itself.

9. Sixthly, modern markets are complicated systems, as it depends on a large number of variables. While increasingly complex scientific and mathematical tools are in place to predict its behavior, analysts are of the view that quantum computers are much better suited for the job. One immediate advantage is that the randomness inherent to quantum computers is congruent to the stochastic nature of financial markets. Investors often wish to evaluate the market behavior under an extremely large number of scenarios generated at random. Another advantage the quantum computers offer is in financial activities such as arbitrage that require large number of simultaneous operations which may be difficult for a digital compute to handle.

10. Seventhly, weather forecasting is similarly a complex task, as it depends yet again on a large number of variables. It is difficult to be exact with predictions, especially when the weather is subject to rapid changes and the information available is limited. Advance warnings of wild weather are necessary to minimize the impact of catastrophic events and the ensuing devastation and loss. The models currently in use are by and large making successful weather predictions but the computing power necessary to keep an eye on the whole global scenario and make more accurate predictions is as yet not available. Many of the world’s
largest supercomputers are already dedicated to weather forecasting but in order to achieve greater accuracy, they need even more computational power. That is where quantum computers are going to be of help.

11. Eighthly, another application of this exciting new tool might be in studying particle physics. Models of particle physics are often extraordinarily complex, confounding pen-and-paper solutions and requiring vast amounts of computing time for numerical simulations. This makes them ideal for quantum computation and scientists have already been taking advantage of this. Quantum computers can be programmed to perform simulations to get an idea about the results of actual experiments. Quantum computers cannot replace the experiments that are done with particle colliders. However, by developing quantum simulators, scientists would be able to understand and predict these experiments with much better accuracy.

12. Ninthly, yet another application of quantum computers is in the field of machine learning and artificial intelligence (AI) where the  quantum AI algorithms, being much more efficient in performing computations than the classical AI algorithms,  is all set to boost its output several times over. AI is based on the principle of learning from experience, becoming more accurate as it keeps getting feedback, until the computer program starts exhibiting ‘intelligence’. This feedback is based on calculating the probabilities for many possible choices, and so AI is an ideal candidate for quantum computation.

13. While quantum computing is already impacting the fields mentioned above, the list is by no means exhaustive, and that’s the most exciting part. As with all new technology, unimaginable applications will be developed in future as the hardware continues to evolve and create new opportunities and openings. Sooner
than later, quantum computers are going to become a reality. Already, Google has claimed that they have a D-Wave 2X Quantum Computing System which is 100 million times faster than any of today’s systems. 

14. USA, China, Europe, Russia and Japan as well as tech giants like IBM, INTEL, Microsoft and Google are the leaders in the field of research in quantum computers and have committed large investments. India has been a late starter but has now has begun preparations to build a quantum computer of her own. Work is being done on superconducting quantum devices in the Quantum Measurement and Control (QuMaC) Laboratory in the Tata Institute of Fundamental Research in Mumbai. The group started work in December 2012 and has demonstrated the working of a three-qubit quantum processor called the ‘Trimon’. It is a baby step as the Google has claimed to have already developed a 72-qubit processor called Bristlecone. The Department of Science & Technology (DST) has set up a programme called Quantum Enabled Science & Technology (QuEST). The DST held its first meeting at IIIT Hyderabad (Jan.8-9, 2019) to discuss QuEST. As part of Phase-I of the programme, the DST will invest Rs.80 crores over a span of three years to facilitate research in this field. In Phase-II, after three years, the ISRO, DRDO and DAE are to review progress and invest another Rs.300 crores to push QuEST further.

15. However, India’s National Cyber Security Coordinator, Lt Gen Rajesh Pant, feels that not enough is being done. He recently expressed (Dec.2, 2019) grave concern over lack of cyber infrastructure in India. He said that sufficient efforts were not being made in this direction and that there was an absence of quantum roadmap in the country. He further said that 2.5% of the global economy was going down the drain every year due to cyber crime and if India was aiming to become a 5 trillion dollar economy by 2024, it could ill afford to neglect this sector.