Physics: Principles and Problems


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For use with Chapter 24
Magnetic Fields

Coffee Cup Computers
Posted August 3, 1998

Do you remember the first computer you ever used? Compared to the machines today, it was probably pretty slow. Today's computers are incredibly fast and powerful. Still, they have limits. For example, some security codes used today are so complex that even the most powerful supercomputers would take billions of years to break them. However, these codes may not be as effective against the computers of tomorrow. Researchers are working on a new type of computer that could possibly decipher these security codes in about a year.

This new type of computer is called a quantum computer. It takes advantage of nuclear magnetic resonance (NMR) technology, which analyzes the magnetic fields surrounding the nuclei of different atoms. The most common use of NMR technology is in medicine, namely magnetic resonance imaging (MRI). MRIs use magnetic fields to study a patient's body, much like an x-ray or a CAT-scan.

Classical computers use a binary system--a series of 1's and 0's--to store data. Each digit in a binary system is called a bit. Quantum computers treat the nucleus of each atom in a molecule as a bit. These are called qubits. Quantum computers use NMR technology to analyze these qubits.

Scientists haven't yet built an effective quantum computer. In 1996, Neil Gershenfeld, Isaac L. Chuang, and Mark G. Kubinec took the first shot and built a very simple 2-bit quantum computer. They succeeded, but there are many more obstacles before you'll find quantum computers sold in your local electronics store.

When this happens, most likely quantum computers will not look like your average classical computers. Classical computers store their data in magnetic disks; quantum computers read and store data in the molecules of a liquid. Gershenfeld and Chuang point out that a quantum computer might look more like a cup of coffee than the standard computer console.

Use this article and the references below to answer the following question:

Why do atomic nuclei respond to an external magnetic field?

Gershenfeld, Neil, and Chuang, Isaac L. "Quantum Computing with Molecules." Scientific American, June 1998.

The Stanford-Berkeley-MIT-IBM Quantum Computation Research Project. http://feynman.Stanford.EDO/qcomp/


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