Tuesday, December 15, 2009

You Are Using Quantum Mechanics In Your Digital Camera

Well, for most of us, that fact isn't surprising. But, it is still useful to emphasize this in case there are still people out there who thinks that QM is only some esoteric subject area (like all of physics) that has nothing to do with their everyday lives.

This is a well-written article in the Washington Post that shows how a CCD detector that is in digital camera came out of the our understanding of quantum mechanics. The inventor of the CCD won the Nobel Prize for Physics this year.

Getting a digital camera for Christmas? Before you fire it up to capture Uncle Wally's fateful fifth trip to the punch bowl, take a moment to picture this: You've got a genuine scientific marvel in your mitts. In fact, it took nothing less than two Nobel prizes and a revolution in physics in order for you to point and shoot.

Why? Because to take a filmless picture, your camera or camcorder relies on, um, quantum mechanics. In particular, it exploits the fact -- revealed by Albert Einstein himself -- that a beam of light, which behaves like a wave in some circumstances, acts like a bunch of separate particles in other circumstances.

A good article to give to someone who asks you if physics is of any use.



Peter Morgan said...

"Who needs an ego boost when you've mastered quantum mechanics?" -- nice line.

A digital camera, however, is not that good an example for quantum mechanics, insofar as a semi-classical model is possible. Discrete transitions of a CCD can be understood to be thermodynamic transitions between a metastable ready state and an excited state, caused by the electromagnetic field that impinges on it.

The behavior of a CCD in a digital camera is more analogue than that, in any case, since each pixel generates a charge that is converted to a digital signal with between 8 and 16 bit precision. Commercial photo images are not single photon detection.

ZapperZ said...

But do you think the CCD was DESIGNED in the way you described?

Some people have continued to argue that the simple photoelectric effect can also be explained using classical stochastic method. Big deal! When pressed to show how and where such a view are used in analyzing, say, the ARPES spectrum, they go silent! The fact remains that these were "products" of quantum mechanics. When "thermodynamics transitions between a metastable ready state and an excited stated, caused by the electromagnetic field" can produce predictions to make consumer products, I'll pay equal attention to it.


Anonymous said...

Folks: while we're on the subject, would the Illuminati please comment on the need for QFT in order to describe photons? Is the Duffin-Kemmer-Petiau-Ghose formalism, for the QM of spin-1 bosons in the limit of no mass, also acceptable?


Andrew Bennett

Corvallis, OR

W.T."Tom" Bridgman said...

For a little more info on the history of some of these connections, read "The Cosmos in Your Pocket: How Cosmological Science Became Earth Technology" at ArXiV.