# Find special double slit experiment

1. Mar 23, 2005

### meemoe_uk

I once read about a modified double slit experiment where the distance between one slit and the source was different to distance between the other slit and the source. It gave the usual interference result, and showed the common feature of other double slit experiments, equal distances to both slits from the source, was an artifact.

But I can't find any reference to this experiment now. Anyone got any links?

2. Mar 25, 2005

### tdunc

You make a good point, and it just goes to show how closely a 'water two-slit experiment' actually resembles a particle based one in interference pattern results. It gave the usual interference effect but yet the actual pattern is different because the point at which the waves intersect will be further out and the waves from say A will be more spread out than the waves from B when they intersect at a point C therefore different than the normal setup where the waves are almost identical in spread when they intersect at a common point C.

3. Mar 30, 2005

### meemoe_uk

not nessacerally. I didn't quite get my wording exact in my first post.

I say....
Exactly, I meant...

where the distance the photons travel from the source

The experiment I read about used fibre optic cables to take the photons destined for one slit round the block a few times before inserting them though the slit.
The slits themselves were the same distance from the source and the destination.

Still can't find a documentation on the experiement. Hope I didn't imagine it.

4. Mar 30, 2005

### Claude Bile

So, essentially what you are saying is that one source (slit = source for interference purposes) is phase shifted relative to the other? If so, why would this group take an optic fibre around the block, when a quartz plate would suffice to give the phase shift (Coupled with the fact that using such a long piece of fibre would introduce coherence issues)?

This result is well known, all it does is shift the cos^2 pattern in the plane of the screen.

I doubt this group could have published a paper on this result alone (unless the paper is very old). If this paper was indeed published, they must have done something else to warrant publication.

Claude.

5. Mar 31, 2005

### meemoe_uk

No. Phase shift was not their goal.
They wanted to see if a photon-wave would interfere with itself, even though part of it was not in the right place at the right time. i.e. the the part of the wave traveling through the cable would arrive at it's slit much later than the other, but even so, typical interference occured.
The result was showing that getting the wave to hit both slits at the same time wasn't nessacery for interference.

6. Mar 31, 2005

### Claude Bile

So you are saying that a pulse of light was sent and one half of the pulse passed through the slit after the other half, and interference still occured?

That would explain the long length of fibre if that is the case.

Claude.

7. Apr 1, 2005

### meemoe_uk

yep. Ain't that a cool experiment and result? I wish I could find it again just so I can be sure it exists.

8. Apr 3, 2005

### Claude Bile

It sounds like such a simple experiment too.

Claude.

9. Apr 5, 2005

### Edgardo

Hello meemoe_uk,

I think you are talking about "conditional interference", where you have an entangled pair of photons, each photon is incident on a Young double slit.

http://www.loqnl.ufal.br/publications/2000/PRA61023801-1(2000).pdf [Broken]
http://www.sbf1.if.usp.br/eventos/enfmc/xxii/programa/res0771.ps [Broken]

Last edited by a moderator: May 2, 2017