And yet another double slit question thread.

[troymclure]

Ok double slit experiment. Two slits send through one photon which passes through both slits due to wave/particle duality.

So really we have two probability waveforms now don't we? One passing through each slit and creating a wave pattern from the start of each slit. THat's how we get an interference pattern.

Ok so would it be possible to put a box at the beginning of each slit which can trap the photons waveform without causing the probability wave to collapse?

Ie So you have two boxes with a waveform probability inside and they'd now be sort of quantum entangled? Ie If you collapsed the waveform of one then the other would disappear?

 

[Drakkith]

I don't know for sure, but I believe that Once you measure which box the photon is in, it will collapse and be in only one box.

 

[troymclure]

OK that makes sense, after all we only get one photon hitting the wall if there is no boxes so there is only one photon it's just that there has to be two waveform/photons for it to pass through both slits.

At least that's what I thought would happen. Except if it does work like that then couldn't we communicate FTL using entangled photons like this?

 

[Drakkith]

I'm not sure honestly.

 

[DrChinese]

At least that's what I thought would happen. Except if it does work like that then couldn't we communicate FTL using entangled photons like this?

Entangled photons do not normally exhibit interference effects, unlike unentangled photons which do. So nature does not allow FTL signaling that way.

 

[troymclure]

Entangled photons do not normally exhibit interference effects, unlike unentangled photons which do. So nature does not allow FTL signaling that way.

Except shouldn't a photon which is split by the double split experiment, be entangled and have an interference pattern? Hence the double slit experiment?

I'm not really thinking this is a way to communicate FTL (though heh that's ok too^^) but mostly I'm just trying to understand what happens in the double slit experiment.

Photon gets sent from photon emitter. It gets to the slits, previously it was a single waveform of probabilities whose paths covered both slits. Once it reaches the slits the probability wave separates(with only the probable paths through the slits now being taken by the wave) and passes through both slits. We now have two waveforms.

This is how we get an interference pattern... and they should be entangled shouldn't they? Only one photon will ever hit the back of the wall so we don't have two photons just two waveforms. And if you collapse one of the waveforms by detecting which slit a photon passes through then the other wave collapses.

Which means that these two photons are now entangled and in a way which allows FTL... unless I'm not getting something about QM (entirely probable) or we can't hold the waveforms without collapsing them.

 

[DrChinese]

Except shouldn't a photon which is split by the double split experiment, be entangled and have an interference pattern? Hence the double slit experiment?

I'm not really thinking this is a way to communicate FTL (though heh that's ok too^^) but mostly I'm just trying to understand what happens in the double slit experiment.

Photon gets sent from photon emitter. It gets to the slits, previously it was a single waveform of probabilities whose paths covered both slits. Once it reaches the slits the probability wave separates(with only the probable paths through the slits now being taken by the wave) and passes through both slits. We now have two waveforms.

This is how we get an interference pattern... and they should be entangled shouldn't they? Only one photon will ever hit the back of the wall so we don't have two photons just two waveforms. And if you collapse one of the waveforms by day detecting which slit a photon passes through then the other wave collapses.

Which means that these two photons are now entangled and in a way which allows FTL... unless I'm not getting something about QM (entirely probable) or we can't hold the waveforms without collapsing them.

You are mixing terms. Entangled photon pairs consist of 2 complete photons essentially sharing one wave function. The double slit does split the input source but you don't call that entanglement. There is one wave function and one photon.

 

[troymclure]

OK cool, that make sense. Wasn't sure if they'd count as entangled. Except... we do have two waveforms right? That's how we get an interference pattern.

I know they're one original waveform but the pattern they make is indistinguishable from two waveforms. Ie The experiment gives us the semblance of two waveforms and could we use that semblance for other things? Could you hold both half waveforms in a state of non-collapse like we do for other quantum sized objects?

Basically put a non-collapsing storage container at both slits. You should have half of the waveform in that storage container now. Well half of the probable locations of that waveform. You could then send one to the other side of the world and collapse it causing the other waveform to also collapse. This should be a non-local event because there is only one photon.

What is the term for those waveforms?

 

[troymclure]

Update: Actually just thinking, it won't be a way to communicate FTL because the photon is only in one box isn't it? There are two waveforms but if you check one of the boxes you'll only find the photon there 50% of the time. Which means you can't use it for communication.

waveform /= photon.

 

[Drakkith]

There isn't a way to communicate because there is only 1 photon and 1 wave function. The wave function IS the photon.

 

[troymclure]

There isn't a way to communicate because there is only 1 photon and 1 wave function. The wave function IS the photon.

Ok so the wave-function is the photon... but we can split the wave-function into two separate holding containers still can't we? And there would be a 50% chance that each container holds a photon. But a 100% chance that each container holds a wave-function. Right? (cause if you released the wave-functions they could still cause an interference pattern as if there were two wave-functions)