Quantum-Nano Computing

Quantum Theory and Nano Technology are natural partners with great potential applications in the context of Computing Systems. Ironically, although the quantum theory is almost emerging as the most successful theory ever proposed in the scientific literature (often accurate to within one part in 10 billion), it can give only probabilities of any object, existing as the superposition of many possible states, rather than definite hard answers to problems as expected from Newtonian theory of "objective reality" in which each object existed in a definite state. However, we have nanotechnology and can manipulate individual atoms, so atoms that pop in and out of existence can be manipulated at will, using scanning tunneling microscope. Accordingly, there should be no invisible "wall" separating the microscopic and macroscopic world but rather a continuum.


One of the best descriptions of the field is the classic talk that the great physicist, Richard Feynman gave on December 29th 1959 at the annual meeting of the American Physical Society at the California Institute of Technology (Caltech) :

"If we wanted to make a computer that had all these marvelous extra qualitative abilities, we would have to make it, perhaps, the size of the Pentagon. This has several disadvantages. First, it requires too much material; there may not be enough germanium in the world for all the transistors which would have to be put into this enormous thing. There is also the problem of heat generation and power consumption; TVA would be needed to run the computer. But an even more practical difficulty is that the computer would be limited to a certain speed. Because of its large size, there is finite time required to get the information from one place to another. The information cannot go any faster than the speed of light---so, ultimately, when our computers get faster and faster and more and more elaborate, we will have to make them smaller and smaller. "

Quantum computers will perform computations at the atomic scale. We might ask how close conventional computations are to this scale already? Figure shows a survey made by Keyes in 1988: The number of dopant impurities in the bases of bipolar transistors used for digital logic against the year. This plot may be thought of as showing the number of electrons required to store a single bit of information. An extrapolation of the plot suggests that we might be within reach of the atomic-scale computations within the next two decades.

The number of dopant impurities in the bases of bipolar transistors

Conventional computers have been improving in speed and miniaturization at an exponential rate since their earliest days. Clearly there is a bound to our ability to miniaturize conventional electronics and we will likely be touching that limit within the next ten to twenty years. The question is raised, can we continue to expect to see an exponential improvement in performance twenty and more years from now? As we approach some of the physical limits to conventional computational construction we may begin to see a slow-down of this exponential rate. A detailed study of quantum computation may help us understand the fundamental physical limitations upon computation, conventional or otherwise

While quantum information science is a broad and rapidly expanding field, there are a few underlying recurrent themes. The theory of classical information, computation, and communication developed extensively during the twentieth century. Though undeniably useful, this theory cannot fully characterize how information can be used and processed in the physical world - a quantum world. Some achievements of quantum information science can be described as generalizations or extensions of the classical theory that apply when information is represented as a quantum state rather than in terms of classical bits. The well-established theory of classical information and computation is actually a subset of a much larger topic, the emerging theory of quantum information and computation.

There is a worldwide effort in progress to spur nanotechnology and it is receiving increasing attention the world over in the last few years. Next ten years will see nanotechnology playing the most dominant role in the global business environment and is expected to go beyond the billion dollar estimates and cross the figure of $ one trillion. Focused programmes on nanotechnology have been launched by several nations. 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.

India is emerging as a global leader in the nanotechnology field and is a significant player in contributing to the development of new technologies besides carrying out basic research at the frontiers. Former President Dr. A.P.J. Abdul Kalam has envisioned, "Nanotechnology is knocking at our doors. . . Molecular switches and circuits along with nano cell will pave the way for the next generation computers. . . With the emergence of Nanotechnology, there is convergence of nano-bio-info technologies resulting in new devices which has wider applications in structure, electronics, and healthcare and space systems. Potential applications are virtually endless. Progress in nanotechnology is spurred by collaboration among researchers in material science, mechanical engineering, computer science, molecular biology, physics, electrical engineering, chemistry, medicine and aerospace engineering. This is one of the important emerging area which brings synergy in research and development by combining the strengths of the multiple domain knowledge leading to the creation of knowledge society. Our educational institutions and universities should have special purpose missions based on their core competence."

Inspitethe large amount of research and development, there are not many opportunities for exposing our students to these frontier areas. The Quantum and Nano Computing research group at DEI and IIT Kanpur has jointly authored entry level textbooks [1,2] which provide a smooth passage to our students from the classroom to the quantum and nanotech laboratories. The books deal with several issues starting with the basics of quantum and nano computing, qubits, gates, nanotubes, and gradually expose them to the frontline areas of research in these areas.


1. Sahni V., Quantum Computing, McGraw Hill Education (Asia), 2007, ISBN 978-007062095-7.

2. Sahni V., Goswami D., Nano Computing, McGraw Hill Education (Asia), 2008, ISBN  978-007024892-3.