Computer Technologies

 

Emerging Computer Technologies

Progress in miniaturization and computing power in recent decades has been impressive. But there are physical limits to the ways electrons can be shunted around tiny circuits in a wafer of silicon. For this reason, researchers have been looking into alternative technologies that might someday deliver performance unthinkable with traditional semiconductors. Some of the most interesting approaches deal with the very small—the world of molecules and the even more minuscule subatomic realm where the strange laws of quantum mechanics come into play.

Molecules

Among molecules with a high profile in computer- technology research, the two most intriguing are the carbon nanotube and DNA (deoxyribonucleic acid), the basic vehicle of heredity in the biological world.

Nanotube Devices: Carbon nanotubes have a simple structure and astounding physical characteristics. They consist of carbon  atoms, which may be arranged in a hexagonal pattern—like chicken wire. This chicken wire structure is rolled up to form a tube that may be as narrow as 1 nanometer. (A nanometer is one-billionth of a meter, or 0.0000000000254 inch, that is, about 50,000 times thinner than a human hair.) Carbon nanotubes are extraordinarily strong and hard. They are resistant to heat, cold, magnetism, and radiation. Depending on how their atoms are arranged, they can be fine conductors of electricity or, conversely, they may resist its flow. The tiny tubes potentially offer a way to overcome the limitations of the silicon chips and copper wires used in today’s computers.

Engineers have already developed carbon nanotube transistors that can carry as much as 1,000 times the current accommodated by the copper wires used in silicon chips. Today’s computer processors, however, may have a billion transistors or more. Still to be solved are the problems of how to make similarly enormous numbers of high-quality nanotubes and how to arrange them in circuits—while keeping costs down.

Nanotubes’ potential is enormous. Their use incomputer storage and memory devices raises the prospect of ultra-high capacity hard drives as well as fast random-access memory (RAM) that, unlike today’s RAM chips, would not lose its contents when the power is turned off. Such storagedevices could make possible instant-booting computers, handheld computers with upwards of 10 gigabytes of memory, and MP3 players that hold exponentially more songs than today’s devices.

DNA Computing: DNA carries a living organism’s genetic code. Instead of the 0 and 1 used in computers’ binary code, the genetic code uses four basic units called bases, which pack a lot of information into a single strand of DNA. They are usually symbolized A, C, G, and T. In an organism, this information is used, with the help of RNA (ribonucleic acid, a molecule related to DNA) and enzymes, to make proteins as well as replicate DNA molecules. Researchers who would like to employ DNA in computing see particularly great potential in using multiple DNA molecules “in parallel,” thereby generating enormous

computing power, since a trillion or more strands of DNA could be contained in a space as small as a drop of water.

The first demonstration of the manipulation of DNA to solve a simple mathematical problem was made in 1994 by University of Southern California computer scientist Leonard M. Adleman. In 2001, researchers at the Weizmann Institute of Science in Israel created a test-tube computer able to do elementary computations; DNA played the role of software governing the action of enzymes (the “hardware”).

Aside from its rudimentary capabilities, this test-tube computer was rather impractical because accessing the results required substantial equipment. To get around this limitation, the Israeli scientists developed a computer that would not only compute but would act on the results. In 2004, they reported the creation of a DNA test-tube computer that could  detect the presence of cancer genes and thereupon release a drug. Meanwhile, in 2003 a pair of U.S. scientists developed the first interactive DNA computing system, an enzyme-driven device called MAYA that played unbeatable tic-tactoe. Its human opponent made moves by putting DNA into little wells making up the game board; each well contained enzymes that acted as “logic gates” controlling the device’s response to the input data.

Quantum Effects

Much of the buzz associated with quantum computing in recent years has been about computing systems that take advantage of the peculiarities of quantum mechanics to implement parallel processing on an extravagantly huge scale. Conventional computers operate in a binary universe where statements are either true or false, switches are either on or off. In this universe, the bit, the basic unit of information, has a value of either 1 or 0. In the quantum world, a quantum bit, or qubit, can be both on and off at the same time. The two states are said to be “superposed.” Because of this simultaneity of values, a quantum computer using 300 qubits could, in theory, speedily carry out more calculations than the number of atoms in the known universe.

Scientists working to build a practical quantum computer have to confront a number of difficulties. For example, there is the question of how to physically implement qubits. Another big issue is how to extract the results; in the quantum world, the mere act of observing or measuring can cause superposed states to collapse into one state. The first demonstration of a working quantum computer was carried out by California researchers in 1998. The experimental device had just two qubits: the carbon and hydrogen atoms in a molecule of chloroform, which were manipulated with a variation on the magnetic resonance imaging used in medicine. Subsequent quantum computing experiments have been done with slightly more qubits, but the problems solved by the devices have been only rudimentary. A variety of methods have been proposed for constructing quantum computers, including, recently, the use of carbon nanotubes as mechanical qubits.

Cryptography of the Future

Today’s encryption systems for protecting information transmitted via such channels as the Internet tend to rely on mathematical problems that would take an enormous — hopefully unfeasible —amount of time and effort to solve. For example, one of the most popular encryption methods, called RSA (from the initials of its inventors), depends on the fact that it is very hard to find the prime factors of a very large number—that is, the prime numbers that produce the number when multiplied by each other.

This approach works for now, but what if mathematicians make a breakthrough? As it happens, one of the most celebrated unsolved problems in mathematics, the so-called Riemann hypothesis, deals with the pattern that might lurk behind the seeming randomness of prime numbers.

Another potential threat to secure encryption comes from quantum computing. In 1994, Bell Laboratories computer scientist Peter Shor demonstrated that a sizable quantum computer, because of its unconventional properties, could find the factors of a large number reasonably quickly.

Paradoxically, quantum physics could also become thesavior of secure encryption. Socalled quantum cryptography, whose origins date back to the late 1980s, utilizes such fundamentalquantum concepts as the Heisenberg uncertainty principle (it is impossible to measure one property of a quantum system without perturbing a second one) and the principle of entanglement (two separate quantum systems that interacted at one time may still share some information). The keys required for encrypting and decrypting messages are represented in this instance by a pattern

of particles of light, or photons, with certain characteristics. Interception by an eavesdropper will leave obvious traces, revealing that the key has been detected.

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