Can someone explain the details of the delayed choice quantum eraser experiment?

Question

http://www.bottomlayer.com/bottom/kim-scully/kim-scully-web.htm

I would think a message could be transmitted faster than the speed of light based on whether or not an interference pattern developed.

Answer 1

interesting, thats the first i've read of that. I'm familiar with the two-slit experiment they refer too, which basically is one of the best example of the wave-particle duality that exists in quantum mechanics, ie particles at that level behave like both waves and particles. The premise is that you can fire individual electrons at the two slits, and the paths that are taken are not what you would expect from a point particle, but rather behave like a wave, interferring with each other like waves do, but we know we fired single electrons...basically the paper you cited says that they think they found a way to measure electrons as point particles rather than waves. ok here it goes...as basic as i can think of it is this...observing the particles makes them behave like particles. If we dont observe them they behave like waves. The experiment basically observes the particle as it passes through a slit by means of observing its entangled partner, which makes the observed partner behave like a particle, but the other entangled partner still acts like a wave, so the interference pattern created in a normal two-slit experiment doesnt exist in the delayed choice eraser. the delayed choice erasing refers to the delay in erasing the quantum observation in order to make the measurement...hope that makes sense...sometimes i have trouble putting things this complex into words!