Photons and Phools

Like a lot of people, I don't spend a lot of time thinking about photons. For that matter, I don't know that I ever thought much about them, which might have something to do with the final grade I got in Physics 101. But it's lucky that people smarter--make that "a lot smarter"--than me do. People like Paul Kwiat and his team at the University of Illinois Kwiat Research Group.

Team Kwiat is primarily interested in optical quantum information processing, as applied to quantum computing and communications. And one thing they've apparently done is crack the concept of "dense coding" as it pertains to photons. As they explain it, in classical coding, a single photon conveys only one of two messages--one bit of information. In dense coding, a single photon conveys one of four messages--two bits of information. That may not seem like a big deal to those of us who sat as far back in the lecture hall as possible, but it is a big deal to researchers studying quantum computing.

"Dense coding is possible because the properties of photons can be linked to one another through a peculiar process called quantum entanglement," says Kwiat. "This bizarre coupling can link two photons, even if they are located on opposite sides of the galaxy." The bottom line: Understanding dense coding means that lots more information can be sent back and forth and correctly decoded in the process. You can find out more in Beating the Channel Capacity Limit for Linear Photonic Superdense Coding by Julio T. Barreiro, Tzu-Chieh Wei, and Paul G. Kwiat. (Fee required.)

But Team Kwiat isn't the only research group examining issues related to photons. Researchers at IBM have an ongoing project called Silicon Nanophotonics that, because it involves photons, optics, and the word "dense," seems somehow related, albeit from a different perspective. The goal of Silicon Nanophontonics is to develop a technology for on-chip integration of ultra-compact nanophotonic circuits for manipulating the light signals, similar to the way electrical signals are manipulated in computer chips. Integrating optical devices at the chip level lowers the cost of optical components. Moreover, dense photonic integration might enable a new area of optical interconnects also at the chip level.

*Sigh* At times, I wish I'd paid more attention--and less fooling around--in class.

-- Jonathan Erickson
jerickson@ddj.com

Posted by Jon Erickson at 03:40 PM  Permalink