Query on use of prism in delayed choice quantum eraser experiment

[Steve4Physics]

TL;DR

Query on use of prism in delayed choice quantum eraser experiment

Hi. I’ve seen a number of schematic diagrams for the Delayed Choice Quantum Eraser experiment. Some include a prism to make the two idler photon paths diverge.

However, the prism is shown refracting the ‘idler rays’ in a way which contravenes Snell’s law. E.g. see prism marked ‘PS’ (not the Glan-Thompson prism) here:

(from https://en.wikipedia.org/wiki/Delayed-choice_quantum_eraser)

Is this a mistake or have I misunderstood something? Thanks.

 

[Drakkith]

However, the prism is shown refracting the ‘idler rays’ in a way which contravenes Snell’s law. E.g. see prism marked ‘PS’ (not the Glan-Thompson prism) here:

Hmmm. I doubt the prism in the diagram is supposed to show the actual path of light in the experiment.

 

[Steve4Physics]

Hmmm. I doubt the prism in the diagram is supposed to show the actual path of light in the experiment.

Yes. It seems that part of the diagram is a bit of a 'bodge'. But the rest of the diagram seems OK. But I've found similar diagrams showing the same thing, so it's very puzzling.

 

[Drakkith]

No one is worried about Snell's law when they're throwing shapes and lines into powerpoint.

 

[Steve4Physics]

No one is worried about Snell's law when they're throwing shapes and lines into powerpoint.

I guess so. But it's much more than a minor misjudgement of angles.

And I noticed another mistake in the diagram. The ray paths through the Glan-Thomson prism (just after the SPDC non-linear crystal) are wrong.

Maybe I'm just being too picky!

With a bit of searching (using Google Images) I've now found a diagram which appears correct. I’m not sure about copyright so here's just the link:
https://www.researchgate.net/public...-delayed-choice-quantum-eraser-experiment.ppm

 

[quad rant]

In the original paper, the the distance between the two slits is 0.7mm. The paper shows that the prism sorts the idler photons coming from A or B. How is this possible? I mean, due to the wave nature of light, the prism should not be able to do this. But, the whole experiment depends on the prism being able to do this. I think photons from A or B should hit either side of the prism about equally as often.

 

[Nugatory]

In the original paper, the the distance between the two slits is 0.7mm. The paper shows that the prism sorts the idler photons coming from A or B. How is this possible? I mean, due to the wave nature of light, the prism should not be able to do this. But, the whole experiment depends on the prism being able to do this. I think photons from A or B should hit either side of the prism about equally as often.

It's not "light", it's single photons and .7 mm is four orders of magnitude more than the 350 nm wavelength of the photons. They can easily resolve a .7mm feature.

 

[quad rant]

Why do I even bother? I should have checked Quora first. My bad.

 

[DaveC426913]

Is this a mistake or have I misunderstood something? Thanks.

It is not a blueprint; it is a schematic.

The prism is nothing more than an icon, a symbol: "here be a refracting prism. The astute reader knows how they work."

Notice these components are mere schematic symbols too:

They don't really physically do that.


Likewise, in network schematics, "the cloud "is not really shaped like a cloud. And databases are not really shaped like oil drums.