I recently tried a "DIY Quantum Eraser" experiment that was in the May 2007 issue of Scientific American (http://www.scientificamerican.com/article.cfm?id=slide-show-do-it-yourself-diy-quantum-eraser"). The basic idea is it's a double-slit experiment where photons going through each slit are "marked" by linear-polarizing the light at a right angle relative to the other slit, then "erasing" the marking by introducing a 45-degree polarization. It worked well, but I had trouble believing that I was witnessing a true "quantum eraser" effect. It struck me that two light waves, linear-polarized at right angles to each other, perhaps would not interfere regardless of the circumstances. A little digging online and I found the http://encyclopedia2.thefreedictionary.com/Fresnel-Arago+laws" [Broken], which state that light polarized at right angles does not interfere. I looked all over for someone pointing out SciAm's error, but found nothing. A few people have written about performing the experiment, but none protested that the observed results aren't what they are purported to be. Am I right in assuming that Scientific American got it wrong -- that this experiment confirms not quantum erasure, but the Fresnel-Arago laws? Or, is it that the Fresnel-Arago laws predate quantum mechanics, and quantum erasure actually explains why two orthogonally polarized beams will not interfere?