Imagine a computer with the power of your desktop or laptop that could fit in the palm of your hand. Imagine tiny, computer-controlled robots performing medical maintenance from within your bloodstream. This is all possible with the development and enhancement of quantum computers. Quantum computers are computers whose components are subatomic particles that have been individually manipulated to store data. Such small computers make it possible to create machines on the order of a billionth of a meter in size. In their article, A Simulator for Quantum Computer Hardware (2002), Kristel Michielsen and Hans and Koen De Raedt discuss a new computer program called the “Quantum Computer Emulator” which simulates the components that make up a quantum computer and allows researchers to test the processing speed, memory, and size of hypothetical quantum computers in a virtual setting. By simulating a quantum computer, the emulator tests quantum computers and shows the promise that they have for revolutionizing computer technology.

The size of quantum computers is the physical limit on small microprocessors because their processors are made from individual elementary particles. This is because the components of a quantum computer are individual atomic constituents, such as electrons, rather than transistors which are made of many atoms. Conventional computers are made up of processors which themselves have millions of tiny transistors. Information, such as data, software, and programs, are put into a computer via binary code through various computer languages which all translate down to bits at the most basic level. A “bit” is a 1 or 0 corresponding to a transistor that is either on or off within the processor. Up to the present, silicon processors have improved according to Moore’s Law, which states that “as the size of transistors shrink, the number of transistors contained on a given chip would double every 18 to 24 months” (McDonald 1). From this trend, “many experts believe that science will hit a wall at some undetermined point in the future” (McDonald 2).

Quantum computers offer a way to avoid this wall. Rather than containing transistors made of many atoms, the “transistors” of a quantum computer are even smaller than a single atom. The basis for bits in a quantum computer is due to a quantum mechanical property called “spin” (Michielsen 23). According to quantum mechanics, every fermion (e.g. electrons, protons, neutrons, and others) have a property called “spin.” Only two types of spin are allowed , spin up and spin down, and these two conditions are what make up quantum computer bits, or qubits, much like the 1’s and 0’s in conventional computers (23). In this way, transistor circuits are replaced with elementary particles possessing spin.
In their article, Michielsen and the De Raedts discuss a computer program which models the hardware of a quantum computer and mathematically models the behavior of quantum mechanical spin (Michielsen 23). The spin of particles can be determined and manipulated probabilistically to form binary bits of information. The Pauli Exclusion Principle is used to manipulate the spin of the particles. It states that no two fermions can occupy an identical state at the same time. Therefore, by bringing control particles with predetermined spin into proximity with target particles, the spin of the target particles can be manipulated to form a binary code and information can be stored (Michielsen 25-27).

The effects on the size of computers from using quantum spin instead of transistors to form binary code are dramatic. For example:

A 10,000 element logic system (enough to hold a small processor) would occupy a cube no more than 100 nanometers on a side. That is, a volume only slightly larger than 0.001 cubic microns would be sufficient to hold a small computer. . . Devices of the size range suggested above (~0.1 microns) would easily fit in the circulatory system and would even be able to enter individual cells (Merkle 4).

Thus, an entire computer could fit inside a space thousands of times smaller than a cell. The ambitious goal using current technology for the size of an individual transistor is over 10 times larger than the size that an entire quantum computer could fit in. Such a quantum computer would also run with a speed only slightly less than today’s Pentium 4 processors (McDonald 2).

The effects of this technology could revolutionize the computer industry in the not so distant future, with ramifications extending to other fields. Primitive quantum computers have already been created that excel at factoring large numbers into primes, a characteristic of many encryption processes. If computers develop at their current rate, more advanced quantum computing should be available “in the 2010 to 2020 time frame” (Merkle 9). After this, it won’t be long until it extends into medicine, where it is feasible that machines the size of blood cells could travel through the bloodstream hunting for and destroying cancer cells or viruses. When computers make the quantum leap, the implications for everyone will be enormous.

Sources:

McDonald T. (2000) Intel Announces Super-Fast Transistors. NewsFactor Network site. Retrieved February 2, 2003, from <http://www.newsfactor.com/perl/story/5970.html>

Merkle, R. C. (1996) Nanotechnology and Medicine [electronic version]. Advances in Anti-Aging Medicine, 1, 277-286. <http://www.zyvex.com/nanotechAndMedicine.html>

Michielsen, K., De Raedt, H., & De Raedt, K. (2002) A Simulator for Quantum Computer Hardware [electronic version]. Nanotechnology, 13, 23-28.