Monday, February 20, 2012

Quantum computing

The Vancouver Sun reports from the annual meeting of the American Association for the Advancement of Science, held in Vancouver over the weekend, about the state-of-the-art in quantum computing.

Here's the basic idea behind it:  Instead of representing the digital 1 and 0 of the computer by the "on" and "off" states of a transistor, you represent them by something like the two spin states of an electron, spin "up" and spin "down."  As you know, the general state of an electron is a superposition of these two states.  This would correspond to a superposition of a 1 and a 0.  The computer could compute on both values at once.  A string of 1s and 0s would be a series of electron spins, superpositions of 00010101, 00010111, 00010001..., an exponentially large number of possibilities going at the same time.

It's not often you come across a field at the cutting edge of experiment and theory, where the practical applications are within reach.  The folks at D-Wave started selling some sort of primitive ($10,000,000) machine last year, to much controversy.  You might enjoy Scott Aaronson's blog wrap on D-wave (dated by a few years). It's a window into the practice of science and the competing priorities of academic and industrial researchers.

Hopefully we can discuss quantum computing in more detail later, either online or in class toward the end of term.  If I could choose my path in physics all over again...?? 

Oh, and the New York Times reports yesterday on a transistor created from a single phosphorus atom.

1 comment:

  1. So is spin up valued as a '1' and spin down is valued as a '0'? Also, if there is a superposition of 00010101, does the order of the numbers have any chronological value? I'm having trouble understanding what a series of spin up's and down's means. Or does the combination of the two describe the electrons superposition?