Question about the Which Way experiment & the detectors used

In summary, the Which Way / Quantum Eraser Experiment is a demonstration of the wave-particle duality using photons. You can use polarizing filters to detect which slit the photon went through.
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L1ght
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What detectors are used in the which way (double slit) experiment and why aren't there videos showing the results of an actual which way (quantum eraser) experiment ?
Hello,

I have a question about the Which Way / Quantum Eraser Experiment.

I have tried my best to research online before coming to this forum to ask questions, so I apologize in advance if this question is novice but I have researched.

I have been looking for a YouTube "video" of a real world double-slit experiment that incorporates an actual "which way" detector (before of after the slit) monitoring which slit the particle travels through. YouTube has hundreds of double slit experiments but none show an actual live video of a detector collapsing the wave function. All of the video examples that I have observed (pun intended) that switch from "observed to unobserved" state are purely lecture based and not a live video. They simply show a graphic image of a camera/detector and how the detector (observer) theoretically collapses the wave function.

I am setting up a lab to conduct a few double slit experiments with and without observation and would like to get some ideas and feedback on the following:

1.) What kind of detector should I use that would record the particle path and collapse the wave function ?
2.) For the particle test, I will try experimenting by sending single photons using optic attenuators, but what can I use to record the collective single photon (particle) buildup test as is seen on many of the videos ? The examples I have seen appear to be software based displayed on a monitor.

Thanks in advance and sorry if these questions are novice.

Mike
 
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  • #2
L1ght said:
2.) For the particle test, I will try experimenting by sending single photons using optic attenuators, but what can I use to record the collective single photon (particle) buildup test as is seen on many of the videos ? The examples I have seen appear to be software based displayed on a monitor.
For detecting photons any digital camera sensor can do that job. Grab a used handheld camera if you just want something cheap (be sure to get one with a removable lens if you need it for your setup), or spend a lot more for a cooled, low-noise CCD or CMOS sensor used for astronomy or other low-signal tasks.
 
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Drakkith said:
For detecting photons any digital camera sensor can do that job. Grab a used handheld camera if you just want something cheap (be sure to get one with a removable lens if you need it for your setup), or spend a lot more for a cooled, low-noise CCD or CMOS sensor used for astronomy or other low-signal tasks.

Thank You ~

What type of test equipment should be used to collapse the wave function simply by observing ?

I have setup a DS experiment in my lab with green laser, it works great and I created 2 good videos. No problem.

I now want to transition from the Double Slit experiment to the wave function collapse by monitoring/observing/detecting/recording, etc... but I do not know what piece of test equipment changes the result simply be observing.

My iPhone camera was able to capture & record the double slit experiment without changing the result or collapsing back into the particle formation.

Do I have to use a specialized detector focused directly on one particular slit in order to demonstrate this collapse ?

Thanks in Advance,
Mike
 
  • #4
L1ght said:
What type of test equipment should be used to collapse the wave function simply by observing ?
That I can't help you with. Photons are very difficult to observe without absorbing them and I don't know how modern experiments get around this.
 
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Thank You
 
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L1ght said:
but I do not know what piece of test equipment changes the result simply be observing.
You can put polarizing filters behind each slit. When the filters are both aligned in the same direction, photons reaching the screen will be in a superposition of "polarized on axis, went through left slit" and "polarized on axis, went through right slit" and will show self-interference. Rotate one filter so that each photon is "marked" according to which slit it went through and the pattern disappears.

If you think about this enough, you'll see that although it makes a much better demonstration it's really not any more amazing than just putting a brick in front of one of the slits... Which brings us to an often-misunderstood aspect of the quantum double slit experiment. The interesting thing is not that the pattern appears or not according to whether which slit is known/detectable. The interesting and uniquely quantum thing is that:
a) The pattern builds up a dot at a time when we use photons, not what we expect of a wave.
b) There is a pattern when we use electrons or other particles, not what we expect of particles.

(You might also take a look at Kim's delayed choice experiment. This technique for detecting which slit an electron went through is unfortunately far beyond the reach of any any amateur lab)
 
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L1ght said:
What type of test equipment should be used to collapse the wave function simply by observing ?
From a theoretical perspective wave function collapse is part of some interpretations of the mathematics of QM. It's not a physical thing.

And, more generally, collapse simply means change irreversibly based on some interaction or measurement.

Also, photons are relativistic particles and, strictly speaking, aren't described by standard non-relativistic QM. They are described by QED or QFT.

In general, therefore, you can't take the wave function collapse too literally. The example @Nugatory gave about polarisation exemplifies this.

That said, I'm impressed by your experimental efforts.
 

Related to Question about the Which Way experiment & the detectors used

1. What is the Which Way experiment?

The Which Way experiment is a thought experiment in quantum mechanics that explores the concept of wave-particle duality. It involves sending a single particle, such as a photon, through a double-slit apparatus to see if it behaves like a wave or a particle.

2. How does the Which Way experiment work?

In the Which Way experiment, a single particle is sent through a double-slit apparatus, which consists of two parallel slits. On the other side of the slits, there are detectors that can measure the position of the particle. The particle can either behave like a wave, passing through both slits and creating an interference pattern, or like a particle, passing through only one slit and creating a single line on the detector.

3. What are the detectors used in the Which Way experiment?

The detectors used in the Which Way experiment are typically photodetectors, which can detect the position of a single photon. These detectors are placed behind the slits in order to measure the path of the particle.

4. Why is the Which Way experiment important?

The Which Way experiment is important because it demonstrates the concept of wave-particle duality in quantum mechanics. It shows that particles, such as photons, can behave like waves and exhibit interference patterns, which goes against our classical understanding of particles.

5. What are the implications of the Which Way experiment?

The Which Way experiment has significant implications for our understanding of the fundamental nature of particles and the laws of quantum mechanics. It challenges our classical understanding of particles and raises questions about the role of observation and measurement in determining the behavior of particles.

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