Recent content by bruce2g

Radio broadcast on "How the hippies saved physics" Sun Sept 18 radio broadcast featuring MIT prof and book author Dr. David Kaiser, Fred Allen Wolf and Jack Sarfatti, at http://bayradio.com/ksfo_archives/?d=0#" - first hour is at 10 PM, second hour is at 11 PM, right click the pop-up player to...

So QE@H is the same as the first setup in the Walborn paper at http://www.fsc.ufsc.br/~lucio/2003-07WalbornF.pdf : laser->double slit->QWP->H polarizer-> screen (except they use a laser, and you polarize after the screen). I'm not sure you'll get interference if the source is not...

Actually, after additional reflection, I think the xts experiment will work. If the Nicol's prism PBS is oriented at 90 degrees, then the P beam will be polarized horizontally, so it will be detected through a horizontal polarizer, and the S photon will be 90 degrees and the QWP's will not mess...

Walborn et al have a more approachable article entitled "Quantum Erasure" available at http://www.fsc.ufsc.br/~lucio/2003-07WalbornF.pdf" . It first appeared in American Scientist, and is targeted toward a technically literate audience, but leaves out the Dirac brackets. They first describe...

Actually, the dcqe in Greene's book isn't the one with 1/4 wave plates, it's the other one, where a beam splitter 'erases' the which-path information in the idler photons. It's important to note that there is a classical connection (a wire) between the idler detectors and signal detectors...

Entanglement is also used in one form of quantum cryptography - Anton Zellinger notes that "In entanglement-based quantum cryptography it leads to the most elegant possible solution of the classic key distribution problem. It implies that the key comes into existence at spatially distant...

One would expect the interaction of the photons with the detector, which is still functioning, to randomly alter their paths, frequency (if there's a collision with a particle involved, which there should be), etc, enough to destroy the interference. I think that it would be easy to debunk it...

Thanks for sending me the files. I'm afraid that since they were scanned, they are each bigger than the 409.6K file size limit, so I can't upload them to the forum. Does anyone know a place where we can park them online?

It's coincidence counting between the signal and idler photons from an entangled beam. The results are in figure 2 of the article, which is at http://grad.physics.sunysb.edu/~amarch/Walborn.pdf Coincidence counting is used for EPR and Bell experiments: if the two photons are detected at the...

PS - They also say "For light generated by spontaneous parametric down-conversion in a nonlinear crystal, the degree of entanglement is controlled by the size of the source (the width of the pump beam) [5,6]. A smaller source size corresponds to reduced entanglement, and therefore to reduced...

Thanks for tracking these down! They are really useful. I can't help but notice that in the first paper (Abouraddy, Nasr, Saleh, Sergienko, and Teich), they do achieve interference by the signal photons if the slits are far enough away from the source (figs 3 & 4). I guess this means that...

http://www.mtl.mit.edu/Courses/6.050/2007/unit10/index.html has some good advice. I especially like this book: "The predictions of quantum mechanics have been verified repeatedly in careful experiments, and the theory has been used effectively in the design of practical systems...

Two points come to mind: First, you could also say, in the DCQE, that registration of an idler at D1 dictates a phase relationship to the coincident signal photons, and that produces the fringe pattern; registration at D2 similarly produces the anti-fringes. Second, it seems to me that if...

gift: good article on entangled photons I have purchased this article and uploaded it as an attachment to this post. I have separately uploaded figure 2, which, for the benefit of RandallB, shows interference with coincidence counting, but absolutely no interference at all for the signal...

This is starting to make a lot of sense. The down conversion introduces a random delay in the photon's journey (when you look at the particle side), but when it does this the crystal also has to completely mess up the coherence of the wavefront as well (when you look at the wave side). So the...