What would happen in this double slit experiment?

TimID

Hi,

I was reading Hawking's "The Grand Design" and I came up with a question I didn't know the answer to. He describes a variant of the two slit experiment with particles where a faint light is shone on the slits to determine which one each particle goes through. Naturally this destroys the interference pattern.

What I was wondering is, if the experiment is set up so that this light is still shone on the slits, but the person observing the experiment is unable to see it (whilst still being able to see the final screen) does the interference pattern form?

Regards,

Tim

mathman

It has been experimentally verified that the interference pattern will form even when the source is emitting one photon at a time.

etamorphmagus

Measurement has nothing to do with humans, but with physical interaction. If there was interaction - decoherence - collpase of the wave function, whatever you call it - then the interference pattern is messed up.

TimID

etamorphmagus: Thanks, thats what I thought, just wasn't sure.