Thursday, March 14, 2013

Feynman's Double Slit Experiment

Either I'm psychic or I have excellent timing in these things.

I showed an illustration of the double slit experiment just a couple of days ago using both single photons and single electrons. Well guess what? Physics World today highlights a modern version of the double-slit experiment using electrons, and supposedly, this one is the closest to Feynman's original thought experiment.

The electrons were created at a tungsten filament and accelerated across 600 V and collimated into a beam. After passing through the double slit, they were detected using a multichannel plate.

The intensity of the electron source was set so low that only about one electron per second was detected – which ensured that only one electron at a time would ever pass through the slits. At this rate it took about two hours for a pattern to build up on the detector – a process that was recorded in real time (see video below). Measurements were repeated with the mask in a series of positions: first blocking both slits, then one slit, then none and then the opposite slit. As expected, the double-slit pattern was seen when the electrons had access to both slits, but not seen when one slit was blocked.

The link shows a video of the accumulation of the signal. You also get free access to the paper since this is a New Journal of Physics article.


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