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    Quantum computing has some truly startling applications

    D. Murali and G. Padmanaban

    Chennai: Quantum computers and quantum information technology remain in a pioneering stage, says Vishal Sahni, author of ‘Quantum Computing’ ( “Currently, there are obstacles to be surmounted, before we have the knowledge to thrust quantum computers up to their rightful position as the fastest computational machines in existence.”

    Quantum systems possess immense computational power due to the startling property of quantum bits (or qubits) that they can exist in a superposition of two or more states at once, thereby opening up immense possibilities like quantum parallelism, quantum entanglement, teleportation, superdense coding and so on, he explains, during the course of a recent e-mail interview with Business Line.

    “The scale of quantum physical phenomena is so vast, that even a super computer built on von Neumann style computing cannot realistically model quantum physics at the atomic and sub-atomic level. On the other hand, quantum computers, which mimic the quantum physics themselves, are capable of vast parallelism and could theoretically simulate such phenomena.”

    Excerpts from the interview.

    How would you define quantum computing in simple terms?

    Calculations like searching the Internet, modeling the national economy, forecasting the weather, strain the capacities of even the fastest and most powerful computers. The difficulty is not so much that microprocessors are too slow; it is that computers are inherently inefficient. Modern computers operate according to programs that divide a task into elementary operations, which are then carried out serially, one operation at a time. Computer designers have tried for some time to coax two or more computers (or at least two or more microprocessors) to work on different aspects of a problem at the same time, but progress in such parallel computing has been slow and fitful. The reason, in large part, is that the logic built into microprocessors is inherently serial.

    A truly parallel computer, in contrast, would have simultaneity built into its very nature. It would be able to carry out many operations at once, to search instantly through a long list of possibilities and point out the one that solves a problem. Such computers do exist and are called quantum computers -- not so much because they are inherently small, but because they operate according to the bizarre rules of quantum mechanics, which do indeed govern the world of the very small: the waves and particles of subatomic physics.

    One quantum rule in particular creates an enormous incentive to apply quantum mechanics to computing: the startling discovery by twentieth-century physicists that elementary particles such as protons, neutrons and electrons can persist in two or more states at once. That makes it possible, at least in principle, for them to be harnessed as processing units in a machine more efficient than any conventionally designed “classical” computer could ever be.

    What are the application areas that can benefit from quantum computing?

    Quantum computing has some truly startling applications, which range from communication to factorisation and searching to teleportation.

    Teleportation is a term that we are all familiar with starting with ‘Star Trek’ in which Spock was teleported all over the galaxy. He was sent from one place to the other without any channel of human travel. Similarly, quantum teleportation is a technique of moving quantum states around, even in the absence of a quantum communications channel linking the sender of the quantum to the recipient. It is quite possible that quantum teleportation and 3-D video conferencing become a reality in another 50 years!

    Superdense coding is another wonderful example of the information processing tasks that can be accomplished using quantum mechanics. in which two classical bits of information can be sent using only a single qubit. The research carried out on quantum computing has created the spin-off field of quantum communication. This area of research aims to provide secure communication mechanisms by using the properties of quantum mechanical effects.

    Peter Shor at MIT has invented a factoring algorithm which when implemented on a quantum computer will crack all cyber-security as we understand it today based on RSA cryptosystem. Another startling result is Grover’s contribution to quantum computation as an efficient quantum mechanical algorithm for searching unsorted databases. That algorithm, discovered in 1996, is faster than any classical algorithm. More than that, it has been shown that no other quantum mechanical algorithm can ever beat it either, i.e., it is optimal.

    Suppose we want to look up a phone number in a telephone directory that has a million entries. Suppose, too, that we have forgotten the person’s name; all the information to search with is an address. In that case, our only recourse is trial and error. On average, we will read the names of 5,00,000 strangers before we find the one we want; on a very bad day, we might have to look at 999,999 of them. Grover’s algorithm solves the problem in just sqrt (N) i.e. 1,000 operations!

    What is the power of quantum computers in comparison to ordinary computers?

    As an example, the largest number that ordinary supercomputers have been able to factor with non-quantum algorithms is “only” 140 digits long. The best classical algorithms would require 10 to the power 24 which would take 1,50,000 years to execute on a Terahertz (10 power 12 Hz) computer. On the other, hand, a quantum computer, using Shor’s algorithm can solve the same problem in 10 power 10 steps, which would execute in less than 1 second on a Quantum THz computer. This is just an insight into some of the startling applications of quantum computing illustrating their immense power and capability.

    How far will quantum computing help in the field of artificial intelligence (AI)?

    The synergy between AI techniques such as soft computing and the emerging areas of quantum and nano computing is imminent while envisioning a holistic view of computing. It is imperative that nanotechnology-based quantum computing would revolutionise computing. Problems that appear intractable at present would be cracked in a matter of seconds.

    The performance of quantum algorithms has proved to be stunning. Artificial neural networks within the context of soft computing have been used for approximation and classification tasks. Quantum neural networks synergise the unique properties of qubits with the various techniques in vogue in neural networks. The improvement in performance over conventional computing problems via this approach is tremendous.

    Quantum neurons have been used for disaster prevention by adopting a hybrid network centric approach with real-time data inputs from several stations to predict the magnitude of disaster at other places. The December 2004 Indian Ocean Tsunami data have been used to verify the algorithm. This approach can be used for advanced warning for other natural disasters like earthquake prediction, volcanic eruptions, aftershock analysis etc.

    Physical realisation of quantum neurons is being pursued at the nanotechnology level through Quantum Cellular Automata (QCA), a very novel nanotechnology that attempts to create general computational functionality at the nanoscale by controlling the position of single electrons.

    Where are we placed in comparison to the US and Europe in research and technology implementation in quantum computing?

    This question is best answered in the words of a great Indian scientist:

    Question (By Dr. Manickam, Pune University): “There is an effort in Europe for secure networking based on quantum computing. Why not such projects be initiated in India?”

    Answer: “A quantum computer is a device that harnesses physical phenomenon unique to quantum mechanics (especially quantum interference) to realise a fundamentally new mode of information processing. Encryption, however, is only one application of a quantum computer. In addition, a researcher has put together a toolbox of mathematical operations that can only be performed on a quantum computer, many of which he used in his factorisation algorithm. Currently the power and capability of a quantum computer is primarily theoretical speculation; the advent of the first fully functional quantum computer will undoubtedly bring many new and exciting applications. Quantum computing is one of the areas, where India can contribute substantially. We are now working on a nanotechnology mission that can make realisable quantum computers. The Conference can debate and make suggestions on how we can bring in synergy in this crucial area.”

    Any guess who answered the question? It was Mr Abdul Kalam, former President of India.

    Focused programmes on nanotechnology have been launched by several nations. For example: the Nanoscience and Technology Initiative (NSTI) in India, and the National Nanotechnology Initiative (NNI) in the US.

    It is estimated that 2 million workers will be needed to support nanotechnology industries worldwide within 15 years. We have to train students, teachers and research scholars. Unless we do this, there will not be enough work happening in this area in the near future.

    What are the latest developments in the field of quantum computing?

    There is a worldwide race to build quantum computers right now, and to show ways to scale the quantum computer to bigger systems with more qubits—just like the microfabrication of conventional chips has given us the impressive gains in conventional computing speed and power.

    The next step is to build the quantum computer bigger and bigger, in the number of qubits. There is still a great deal of work to be done in order to learn how to control the qubits in each technique. It won’t be nearly as easy as it was with conventional computer chips, but at least we know what to do in principle.

    Researchers at the Institute for Quantum Computing (University of Waterloo), in collaboration with MIT, have identified an experimental method to facilitate the design of prototype quantum computers and any other technologies requiring many-body quantum coherence. The quantum process tomography techniques described by them represent a first step toward accurately assessing the powers and limits of these new quantum machines. Indeed, thanks to the techniques developed by a team led by Emerson, we may soon know whether our universe is generous enough to allow for large-scale robust quantum computation.

    What do you see as the future of quantum computing?

    Error correction has made promising progress to date, nearing a point now where we may have the tools required to build a computer robust enough to adequately withstand the effects of decoherence. Quantum hardware, on the other hand, remains an emerging field, but the work done thus far suggests that it will only be a matter of time before we have devices large enough to test Shor’s and other quantum algorithms. It is foreseen that quantum computers will emerge as the superior computational devices at the very least, and perhaps one day make today’s modern computer obsolete. Quantum computation has its origins in highly specialised fields of theoretical physics, but its future undoubtedly lies in the profound effect it will have on the lives of all mankind.

    In sum, therefore…

    As far as the practical implementation aspects of quantum computing are concerned, let me wrap with a quote from Dr. Lov Grover, thus:

    “Will quantum computers ever grow into their software? How long will it take them to blossom into the powerful calculating engines that theory predicts they could be? I would not dare to guess, but I advise all would-be forecasters to remember these words, from a discussion of the Electronic Numerical Integrator and Calculator (ENIAC) in the March 1949 issue of Popular Mechanics: Where a calculator on the ENIAC is equipped with 18,000 vacuum tubes and weighs 30 tons, computers in the future may have only 1,000 vacuum tubes and weigh only 1.5 tons.”


    Dr Vishal Sahni is Lecturer in the faculty of engineering at Dayalbagh Educational Institute (DEI, a deemed university), Dayalbagh, Agra. A graduate in electrical engineering (1999) and an M.Tech. in engineering systems (2001), his Ph.D. was in ‘evolvable hardware systems’ (2004) – all from Dayalbagh Educational Institute.

    Sahni’s current interests are quantum and nano computing systems and applications. He was the convener of the Indo-US Shared Vision Workshop on Soft, Quantum and Nano Computing (SQUAN 2007) organised at DEI in February 2007. The international workshop evolved a roadmap for the future of computing and was host to leading researchers and scientists in the computing field. Among Sahni’s notable contributions is design and development of an Internet-based e-education streaming network for broadcasting multimedia content live to more than 150 stations all over the world.




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