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What in the Heck is "Quantum Computing" Anyways?

The field of quantum computing is a major area or research in physics. Nearly every week a new discovery is made that helps to lay the groundwork for newer developments. But what exactly are quantum computers, and more importantly, how much longer will it be until I can upload my iTunes on to them?

Unfortunatly the answer to the second part is not for a long while. As to what a quantum computers actually are needs a quick look at what quantum physics is.

On the scale of the extremely tiny (we're talking one billionth of a meter and smaller, as in atom sized) particles behave very differently than what we're used to seeing all around us. Fundamental particles, such as photons and electrons, can exist in literally more than one place at a time. Their positions aren't described as a single point, but as a wave of probability, also known as thier superposition. They exist simultaneously at every point along the wave until someone or something measures their location. When this happens, their probability wave collapses, and only then does the particle resolve itself into a single point.

Crazy no? It seems so counterintuitive because were used to looking at large sized objects that obey the "one place at a time" rule we all know and love. In fact what we're seeing is the averages of all the many quantum sized particles, canceling out all but the most probable path an object can take. On the tiny quantum scale, these waves of probability reign supreme. Trials like the famous double slit experiment have physically shown this to be the case. It's not just a particle's path that can exist in many different states at once, but nearly everything that defines it, like its rotation.

So what does all this have to do with computers? The most basic form of information in a computer is a single one or zero, known as a bit. Long strings of bits organized into code are the fundamental language of computer programming. Bits stored in a normal computer are usually magnetized domains on a hard disc. In a quantum computer, subatomic particles would store the bits (known as qbits) of information. The big difference is on a normal computer each bit can be only a 1 or a 0, but in a quantum computer, each bit can be a 1, a 0, or a statistical combination of both a 1 and a 0 at the same time. Because this information exists in many simultaneous states, the quantum computer would be able to run a number of difficult calculations in parallel. To get the final readout one would measure the relevant equation, collapsing the wave functions of all of the other solutions, and yielding a correct answer. By processing all of these equations in parallel, quantum computers could be far more powerful than even the most advanced supercomputers of today. That, in a very brief nutshell, is what quantum computing is all about.

Of course, it's going to be a while before we'll be cruising the information superhighway in the latest qbit powered Pentium-Q processor. Theoretical physicists are still working out how to set up quantum based algorithms while technicians are still developing methods to store qbits. No one knows for sure when the first one of these will hit the markets, but when it does, today's best supercomputers will look like pocket calculators.


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