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One electron - much more information

Physicists plan to break the miniaturization barrier with a completely new breed of computers that operate using electrons rather than electrical signals

Sarah Robinson, New York Times

Berkeley, California. Six years ago, Dr. Peter Shore, a researcher at the T&AT laboratories, sparked an area that was so far obscure in computer science, when he published a recipe according to which a computer whose mechanics is based on the principles of quantum theory could break the coded messages that protect the transmission of data on the Internet.

Since then, top-notch researchers from all over the world have come together to continue to explore how the power of the strange laws that exist in the sub-microscopic spheres can be applied to the computer.

Many governments as well as corporate laboratories such as Microsoft's research division, International Business Machines and T&AT laboratories have already formed a group for them that focuses on quantum computing; Or similar to NASA's research center and the Hewlett-Packard Company (HP), are considering forming such a team in the near future.

An ambitious group located in New York even founded a quantum computing start-up company, called MagiQ Technologies, with the stated goal of establishing a "quantum-based Internet". At a week-long conference held about a month ago at the Computer Science Research Institute in Berkeley under the title Quantum Computing, researchers from academia and corporate laboratories gathered to discuss developments in the field. The talks focused on algorithms for the rapid solution of problems considered impossible in "classical" computers, understanding the limitations of the computing power of quantum-based computers, the approaches to building an applied device and the methods for correcting computational errors.

The conference culminated in a series of lectures intended for the Office of Information Technology in the funding agency of the Federal Department of Defense, which is considering a program to fund quantum computing research. However, although the participants in the conference celebrated the developments in technology, which advanced far beyond the hypotheses of several years ago, they recognize the fact that the researchers are still far from understanding the potential inherent in the technology, its limitations and even further from their goal of assembling an applied device.

Despite this, some of the researchers said that they are attracted to the field, not because of the possibility that one day a quantum computer will be placed on every desktop, but as an opening to a better understanding of the strange world of physics that focuses on quantum theory.

A normal or "classical" computer stores information in units called bits (0 or 1), usually represented by electric currents or volts, which are low or high. In contrast, a quantum-based computer stores information by exploiting the state of elementary particles.

In the classical sense, the electron is a hydrogen atom that may be in a low or high energy level. However, in the strange world of quantum physics, the energy state of the atom is not only high or low, but a balanced combination of the two components at the same time: what physicists usually call a "superposition" of the states. As a result, in some ways the quantum bit contains more information than its classical counterpart. More importantly, as the number of quantum bits increases, the amount of information required to describe them increases squarely.

Classically, since each electron can be in one of two states, a system of 200 hydrogen atoms will be in 1 out of 2 to the power of 200 states (1.6 with 60 zeros after the dot). However, the quantum theory says that at any given moment in superposition, the system may give 2 to the power of 200 possibilities at once.

Since 2 to the power of 200 is a huge number, far beyond the estimated number of particles in the universe, researchers wonder how the universe can keep track of the processes taking place in it. However, the fact that the universe is capable of this hints at the enormous resources of quantum computing power.

"For a small system with 200 atoms, it's as if nature required 2 draft papers to be placed on the side to the power of 200, on each of which a number is written," says Umesh Vazirani, professor of computer science at the University of California at Berkeley, who was a partner in organizing the congress. However, it is difficult to keep track of such a huge database.

According to quantum mechanics, a scientist cannot look at an electron without jolting it out of its delicate superposition and collapsing it into one of its two classical states, according to their weight. The challenge in discovering these algorithms is the application of a lot of hidden information processing power, despite its inaccessibility.

Despite the power inherent in them, said Dr. Shore in his presentation, it is not obligatory that the quantum computers will perform all the operations faster than the classical computers. However, today there are algorithms that make it possible to search databases in the root of the time required for a classical computer.

Such speed is the best possible achievement, according to studies conducted by Dr. Vazirani and others. Their results suggest, he says, that the hardest problem to crack in computing will forever remain beyond the reach of quantum computers. However, Dr. Vazirini points out that these limitations may be a blessing in disguise because they raise expectations for the future development of new encryption systems that quantum computers will not be able to crack.

According to the experts, the main problem in assembling a quantum computer is correcting the accumulated errors during the calculations. Dr. Daniel Gutesman from Microsoft Research examined techniques for correcting some of the errors that occurred during the calculations. According to Gutesman, a breakthrough led by Dr. Schor and his colleagues outlined the general lines for storing quantum states that were stored in memory but partially collapsed due to misdiagnoses.

The many obstacles on the way to a personal quantum computer do not let the researchers down. "What is the value of a new baby that has just been born?" asks Richard Jose, professor of computer science at the University of Bristol, England. "He is still unable to perform any action. But the possibilities are unlimited."

Published in "Haaretz" on 12/03/2000

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