Understanding Measurement Probability in Electron Spin: Explained by Susskind

[rasp]

this is the link.

lecture #4. The question I have is understanding Susskind wording. It is about 13 minutes into the lecture. For example he says, I prepare an electron along the n axis. Then I measure the component of the spin along the m axis. What is the probability if I prepare it along the n axis and measure it along the m axis I will find (through multiple repeated experiments) that the spin is up?

 

[PeterDonis]

lecture #4.

The link you gave goes to lecture #1. I don't see lecture #4 anywhere in that link.

 

[rasp]

Don’t know what’s wrong. Let me try again.

It is 1.54 minutes long lecture 4 in the second series on QM. Subtitled entanglements.

 

[PeterDonis]

lecture 4 in the second series on QM.

I don't see any such series. I just see lecture 1. The "more videos" thing that comes up if I pause the lecture doesn't show any more Susskind lectures.

 

[rasp]

thanks for your patience

I believe I finally got the link. To keep things confused there are 2 different #4 lectures.
[/QUOTE]

 

[andrew s 1905]

It's not a question of "belief". It's a question of not having enough information to even make an evaluation. All you've given me is a vague reference to something said in one of a series of long lectures, and you can't point me to the specific lecture and the specific thing that was said so I can watch it for myself. Nor can you give me a reference to a textbook or paper where the thing you are talking about is described. What am I supposed to do?

Moreover, the real question is not whether you've convinced me of anything, but whether you've given any information that will help the OP. I don't see how you have, since the same issues I raised above also apply for the OP. What is the OP supposed to make of your information?

You make statements all the time without giving references. All I was doing was pointing out that an SG experiment was not being discussed by Susskind. I did this as the multiple references to it might have confused the OP. It is not a difficult technical point that required references it's a matter have having watched the lectures.

Regards Andrew

 

[rasp]

You make statements all the time without giving references. All I was doing was pointing out that an SG experiment was not being discussed by Susskind. I did this as the multiple references to it might have confused the OP. It is not a difficult technical point that required references it's a matter have having watched the lectures.

Regards Andrew

No need to get excited. Andrew is correct Susskind didn’t use SG but used an idealized experiment to describe the probalistic outcomes probably for simplification purposes. However, IMHO, he didn’t provide enough story to correlate the math with the experimental setup.

 

[Nugatory]

Perhaps someone should have asked the OP for the link before assuming it was a SG arrangement.

No one made that assumption. Stern-Gerlach devices came into the discussion because they’re part of the best answer to the question posed in post #9 of this thread. It is not at all clear that the question in post #9 is related (except possibly by confusion) to the material in the linked videos; that question stands alone and is better posed than the question in the original post.

 

[andrew s 1905]

No one made that assumption. Stern-Gerlach devices came into the discussion because they’re part of the best answer to the question posed in post #9 of this thread. It is not at all clear that the question in post #9 is related (except possibly by confusion) to the material in the linked videos; that question stands alone and is better posed than the question in the original post.

I stand corrected. Regards Andrew

 

[PeterDonis]

You make statements all the time without giving references.

When they are reasonably expected to be common knowledge at the level of the thread, yes. But that's not what's at issue here.

All I was doing was pointing out that an SG experiment was not being discussed by Susskind.

In the absence of an actual reference, it's impossible to even evaluate such a statement, as I said. That's why I asked you for a reference, and why I also asked the OP for a reference. The OP has given a reference to a single video and said where in that video he was looking. You have given a "reference" to an entire series of videos, with no information at all about which one you saw or where in that video you saw the statement of Susskind's that you were talking about. So the OP has given the information necessary to evaluate what he is saying. You have not.

Also, you did not just say that Susskind was not talking about an SG experiment. You also made a claim about emission or lack of emission of a photon telling which way an electron's spin was. That is not a claim that can reasonably be expected to be common knowledge. So you need to give a reference to back it up. You haven't.

 

[PeterDonis]

I believe I finally got the link.

I'm very confused. That's the link I had thought was the right one as well after looking on YouTube, and it's titled "Quantum Entanglement", but the whole thing seems to be about special relativity and Lorentz transformations. Am I missing something?

 

[PeterDonis]

That's the link I had thought was the right one as well after looking on YouTube, and it's titled "Quantum Entanglement", but the whole thing seems to be about special relativity and Lorentz transformations.

This link appears to work:

 

[PeterDonis]

This link appears to work

It looks like the PF software is translating the links we post into MEDIA tags, which might end up garbling things. Here is the raw hyperlink I posted, inside a CODE tag to avoid translation:

https://www.youtube.com/watch?v=5vfo512fvlE&list=PLQrxduI9Pds1fm91Dmn8x1lo-O_kpZGk8&index=23

If there are any issues with the embedded video in my previous post, cutting and pasting that link into a new browser tab should go to the right one.

 

[PeterDonis]

IMHO, he didn’t provide enough story to correlate the math with the experimental setup.

After looking at the video I would agree with this; in fact it look like in the 14th minute someone in the audience asks about the experimental setup and Susskind hems and haws and basically says, well, it isn't just one setup, it's a whole range of different experiments and he's just talking about the theory that physicists came up with after considering all of them. So no, he doesn't appear to be talking about any particular experimental setup.