Nanocomputers in Aid of Defense
3.1 Introduction
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Madhuri Sharon, et al. Nanotechnology in the Defense Industry: Advances, Innovation, and Practical Applications, (89–108) © 2019 Scrivener Publishing LLC
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structure can be of microscopic size. The nanoprocessors would have a power and capacity well above the current microproces- sors, with differences so small as to fit on the head of a pin, and therefore would occupy reduced spaces [1].
3.1.1 Classification of Nanocomputers
The nanocomputers fall within the classification of computa- tional nanotechnology, which includes the modeling and sim- ulation of complex structures at the nanometer scale and the management of atoms using nano-manipulators controlled by computers. A nano-manipulator is a specialized micro- scopic and nanorobotic viewing system that helps scientists and researchers working on extremely small objects. The sys- tem was initially designed for microscopic manipulation by computer integration manufacturers. Within the classification of computational nanotechnology are four possible develop- ments of nanocomputers [2]: (i) Electronic, (ii) Mechanical, (iii) Chemical & Biochemical and (iv) Quantum.
3.1.1.1 Electronic Nanocomputers
Electronic nanocomputers contain molecular scale compo- nents, that are likely to be up to 10,000 times more densely inte- grated than today’s smallest microcomputers.
Electronic technology is one of several alternative technol- ogies that have been proposed for implementing a nanocom- puter. Electronic nanocomputers could be of a magnitude faster than current electronic computers, as well as many times smaller or more densely integrated. Although some of the operating principles for electronic nanocomputers could be similar to microcomputers, there is a limit as to how far the designs and fabrication technologies for microcomputers can be scaled down. These devices and designs take advantage of some of the very effects that have been obstacles to making
smaller conventional transistors and circuits. Although elec- tronic nanocomputers will not use the traditional concept of transistors for their components, they will still operate by stor- ing information in the positions of electrons. There are sev- eral methods of nanoelectronic data storage currently being researched. Among the most promising are single electron transistors and quantum dots [3]. All of these devices function based on the principles of quantum mechanics. The number of electrons can be changed by adjusting electric fields in the area of the dot. Dots range from 30 nm to 1 micron in size and hold anywhere from 0 to 100s of electrons [2].
3.1.1.2 Mechanical Nanocomputers
Mechanical nanocomputers would use tiny moving compo- nents called nanogears to encode information. Such a machine is reminiscent of Charles Babbage’s analytical engines of the 19th century. For this reason, mechanical nanocomputer tech- nology has sparked controversy; some researchers consider it unworkable. Eric Drexler and Ralph Merkle are the leading nanotech pioneers involved with mechanical nanocomputers.
They believe that through a process known as mechanosynthe- sis, or mechanical positioning, these tiny machines would be able to be assembled [4].
The fabrication of nanomechanical devices requires some handmade parts. It becomes a tedious job to move a few atoms from one place to another, and it is really a difficult task to man- ufacture a reliable system using this technique.
3.1.1.3 Chemical and Biochemical Nanocomputers
Chemical and biochemical computers would store and process information in terms of chemical structures and interactions.
In general terms, a chemical computer is one that processes information by making and breaking chemical bonds and
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stores logic states or information in the resulting chemical (i.e., molecular) structures. In a chemical nanocomputer computing is based on chemical reactions (bond breaking and forming) and the inputs are encoded in the molecular structure of the reactants and outputs can be extracted from the structure of the products, meaning that in these computers the interaction between different chemicals and their structures is used to store and process information.
Biochemical nanocomputers already exist in nature; they are manifested in all living things. But these systems are largely uncontrollable by humans and make artificial fabrication or implementation of this category of “natural” biochemically- based computers a far-off possibility, because the mechanisms for animal brains and nervous systems is still poorly under- stood. We cannot, for example, program a tree to calculate the digits of π (pi), or program an antibody to fight a partic- ular disease (although medical science has come closer to this idea in the formulation of vaccines, antibiotics, and antiviral medications.
3.1.1.4 Quantum Nanocomputers
A quantum nanocomputer stores data in the form of atomic quantum states or spin. Today’s computer data is in bits, using a binary system in which every bit has a value of either 1 or 0. Quantum computing exponentially expands the potential of computing by applying quantum mechanics, and measur- ing data in qubits instead of bits. Technology of this kind of nanocomputer is already under development in the form of single-electron memory (SEM) and quantum dots. The energy state of an electron within an atom, represented by the elec- tron energy level or shell, can theoretically represent one, two, four, eight, or even 16 bits of data. The main problem with this technology is instability. Instantaneous electron energy states are difficult to predict and even more difficult to control.
An electron can easily fall to a lower energy state, emitting a photon; contrarily, a photon striking an atom can cause one of its electrons to jump to a higher energy state [5].
3.1.1.5 DNA Nanocomputers
DNA computing is a branch of computing which uses DNA, biochemistry and molecular biology hardware, instead of the traditional silicon-based computer technologies. In 1994, Leonard Adleman took a giant step towards a different kind of chemical or artificial biochemical computer when he used frag- ments of DNA to compute the solution to a complex graph the- ory problem [6]. Like a computer with many processors, this type of DNA computer is able to consider many solutions to a problem simultaneously. The first prototype of a DNA com- puter, the TT-100 by Leonard Adleman, was a test tube filled with 100 microliters of a DNA solution. He managed to solve, for example, an instance of the directed Hamiltonian path problem [7].
These computers use DNA to store information and per- form complex calculations. DNA has a vast amount of storage capacity that enables it to hold the complex blueprints of living organisms. A single gram of DNA can hold as much informa- tion as one trillion compact discs [8].