How to Build Your Own Quantum Entanglement Experiment (2013)

https://blogs.scientificamerican.com/critical-opalescence/how-to-build-your-own-quantum-entanglement-experiment-part-1-of-2/

by abrax3141 • 4 years ago

153 37 4 years ago

blogs.scientificamerican.com

verisimi• 4 years ago

Here's part 2:

https://blogs.scientificamerican.com/critical-opalescence/ho...

Simples. So now we can check for ourselves...

jessriedel• 4 years ago

Yes, part 2 is key because it's only when he starts measuring polarization that he demonstrates entanglement rather than just the fact that photons are being emitted in pairs.

dskloet• 4 years ago

The article mentions a photo of the setup ("see photo below"), but I don't see it.

Xcelerate• 4 years ago

This is really fascinating. It would be cool if we had an online group or forum that attempted to brainstorm the simplest/cheapest/(safest?) ways of performing interesting experiments like this that you wouldn’t think you could do at home. I’ve read about a few experiments for determine the speed of light using a microwave that I thought were pretty cool.

hoyd• 4 years ago

A student just now told me about an open source rpi muon detector that can be built at home. That should be added to such a list. I work at Andøya Space.

jahnu• 4 years ago

https://www.youtube.com/watch?v=ejKCiBZwB34

determine the speed of light using a microwave and marshmallows :)

penteract• 4 years ago

I'd like to know whether the frequency printed on the microwave was calculated using the speed of light, in which case you'd just be reversing someone else's calculation rather than making an independent measurement of the speed of light.

tzs• 4 years ago

In an optics class I took in college one day the professor picked up a ruler and said "Let's measure the speed of light". The class laughed, and then he proceeded to measure the speed of light with his ruler.

It was a metal ruler with the distance markers raised. He put the ruler on a table, reflected a laser off the ruler onto the blackboard and got a diffraction pattern, marked the positions of the lines of the diffraction pattern with some chalk, marked the position of the ruler on the table, and then turned off the laser.

Then using the ruler he measured the distance from the mark on the table to the blackboard, and measured the spacing of the lines in the diffraction pattern. It was then a short bit of math later and he had the speed of light.

Of course he had to use the frequency of the laser in that calculation, and the frequency of the laser was almost certainly calculated using the speed of light so in all likelihood all his demonstration actually did was verify that the frequency of the laser was really what the manufacturer said it was.

That then raises the question of whether there is a way we can determine the frequency of visible light without knowing the speed of light.

We could do it for radio probably fairly easily by a method I'll describe below but I don't know if that could be pushed all the way to visible light. On the other radio might be good enough. A 2.4 GHz radio wave has a wavelength of around 12.5 cm. I'd guess that it would be practical to build something that could make a diffraction pattern with that and let you then calculate the speed of the wave just like my professor did, albeit you'd need a lot more room than we had in the lecture hall.

Here's how I'd go about trying to get a radio wave around 2.4 GHz without knowing the speed of light or using anything that depends on knowing the speed of light.

First, I'd build two variable electronic oscillators and adjust them to match the frequency of the D right above middle C on my piano. That's 293.665 HZ.

Then I'd tune one of the oscillators up until it is twice the frequency of the other. You can build circuits that can detect when one oscillator is twice the frequency of another. You can even use those to build feedback circuits to adjust the tuning of the second oscillator to keep it exactly twice the first if either drifts a little due to things such as temperature changed.

Then tune the first to be twice the second. Keep doing this. If you can do this enough to get 23 doublings you'll end up at 2.46 GHz.

You probably can't actually do that with the original two oscillators, at least if you start off with simple EE 101 circuits. You might have to build more sophisticated oscillators along the way.

Actually, it might be best to build 23 oscillators instead of swapping, so you can have the complete chain of frequency doublings available, with each oscillator locked to twice the frequency of a neighbor by a feedback circuit.

To extend this all the way to visible light you'd need 37 to 44 doublings, depending on which piano note you use as your reference.

37 halvings brings visible light down to 2900-5800 Hz. The notes F#7-C8, 2959.96-4186.01 Hz, (82-88 on the standard 88 key piano) are in that range. You can halve visible light up to 44 times and remain in piano range. 44 halvings bring you to 23-45 Hz. The notes A0-F1, 27.5-43, 6535 HZ, (keys 1-9) are in that.

I don't think we have nearly as much flexibility with light as we do with radio when it comes to making variable oscillators and with making things that can detect when one light source is a frequency that is an integer multiple of another, so I don't know if it this method could be extended far enough.

CamperBob23• 4 years ago

There's a neat book called "Exploring Quantum Physics through Hands-On Projects" that is well worth a look, for those so inclined.

https://www.amazon.com/Exploring-Quantum-Physics-through-Pro...

yesenadam• 4 years ago

(2013)

acosmism• 4 years ago

so last year

DecentAI• 4 years ago

TIL that there readily available radioactive material/disks sold online…

quickthrower2• 4 years ago

Smoke detectors have radioactive material

aceazzameen• 4 years ago

Not all though. Photoelectric detectors also exist and seem to be more common in homes these days.

dr_dshiv2• 4 years ago

TIL that you can buy antimatter on the internet.

busyant• 4 years ago

I have taught a chemistry class where we use those disks. They have a stamp on them that say something like "NRC exempt quantity."

So, apparently, the disks have enough radioactive material to detect, but not enough to cause anyone to worry.

dr_dshiv2• 4 years ago

You can create superpositions with guitar strings.

jimhefferon• 4 years ago

Not a physicist, so maybe I have a completely wrong idea. But is not superposition of waves different than (in any event less surprising than) superposition in discrete particles?

alphabetting• 4 years ago

I just played this online Qubit game that I thought I would put down after a few minutes. Ended up playing for 50 min to finish and actually got a much better sense of how quantum computers work than before.

https://quantumai.google/education/thequbitgame

bradrn• 4 years ago

Relatedly, I recently discovered https://algassert.com/quirk — it does require a bit of quantum computing knowledge to use, but the UI is excellent, and I found it incredibly useful for ‘getting a feel’ of how various quantum algorithms work.

Green_man• 4 years ago

This website is incredibly helpful for quick simulation. My favorite design detail is that the circuits are stored in the url, allowing easy bookmarking or sharing of some specific circuit.

lifefeed• 4 years ago

Much happier game than the time I destroyed the universe with paperclip manufacturing.

Nzen• 4 years ago

Thanks for suggesting this game. I can definitely see Townsend's influence, though I prefer his A Dark Room .

How did you make headway with the research project subsystem ?

I've tried submitting just algorithm responses with lots of valid samples, but that doesn't seem to correlate with success. The svelte js for the game is minified, so I couldn't tell what it tested to choose success or failure. Thanks

imglorp2• 4 years ago

Side note, with the invasion scare it's been almost impossible to buy any sort of consumer radiation monitors. Everything is sold out or on backorder.

zabzonk3• 4 years ago

Sorry, what "invasion scare"?

imglorp2• 4 years ago

Are you suggesting there has been no invasion? Anyway they made explicit threats.

https://www.reuters.com/world/europe/russia-warns-baltic-nuc...

yccs27• 4 years ago

The parent is referring to the Russian invasion of the Ukraine, stoking fears of a bigger and possibly nuclear war.

marvel_boy• 4 years ago

Should not have (2013) in the title?

nlarion• 4 years ago

Not sure why, but the article doesn't have the original photos that went along with the post(s):

https://web.archive.org/web/20160919103031/http://blogs.scie...

https://web.archive.org/web/20150926005801/https://blogs.sci...

CamperBob23• 4 years ago

One thing I don't get: he is measuring gamma rays, which will go through the wall of the Geiger tube as easily as they'll go through the front window. Why does it matter how the tube is oriented with respect to the source? Seems like the only factor that should affect the count rate is distance.

anfractuosity• 4 years ago

Has anyone got the book 'Exploring Quantum Physics through Hands-on Projects', it sounds pretty cool

CamperBob23• 4 years ago

It is a fantastic book IMO. Some of it is fairly advanced, although there's never more math than is really necessary to explain what to expect from the experiments. The chapters on recreating the early CRT experiments of people like Hertz, Crookes, and Thomson are especially nifty.

If you wanted to perform most or all of the experiments it will probably cost you at least a few thousand dollars (and a few months' time), but the authors have done a great job with the presentation and content and clearly know their stuff.

How to Build Your Own Quantum Entanglement Experiment (2013)

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