Lecture 5 | Quantum Entanglements, Part 1 (Stanford)

[DaMav]

This is a masterful series up to this lecture which is almost impossible to follow because you can't read the board. What a frustrating hr & 45 minutes. I hope they fired the AV responsible; this isn't exactly rocket science to figure out there's a problem and correct it.

[burridheut]

Trick: To see better what is written on the white board, if you are watching from a laptop, put the lid in an angle of 135 degrees or more related to the keyboard. You will see MUCH better! :)

[grunder20]

give me more so I can understand all of this.

[agapitoflores001]

This one help me a lot in understanding the topic.

[CaptainImpedance]

Mother Matrix=[123456789,246813579,48­372659,876543219,753186429,516­23849] What is the Eigen Vector of this Matrix?

[Hythloday71]

How can he say that the difference between reality being described by vector spaces as opposed to classical logic / set theory is not profound? Clearly set theory gives a sense of immutable reality to our properties where as Vsp's hold no such purity of quantities. It is as if QM sys have a banker/ accounts, so long as the book balances according to the rules - all OK ! With set theory, reality is the banker, an instance of a set member could have 'a watcher' - ie the 'green' ball ...cont ..

[Hythloday71]

@Hythloday71 - 'a' grn ball could be followed and tracked throughout the sys. Now i know,QM says we cannot know exactly due to uncertainty, but the Bell Ineq discussion means abstractly, this prohibition is irrelavent, since nature, it's updates of sys, its allowable configurations of states of spaces, IS DETERMINED by V.sp. theory. This is a pure mathematical mental construct which undermines reality as one might commonly think. Consider the grn ball collide with red .. cont:

[Hythloday71]

@Hythloday71 - classically 2 observers can continually keep track of them, in QM, in an entangled state, the observers can no longer agree about the existence of the grn and red balls, there is a new combined vector state of 'green-blue' ball. In reality we do not consider properties to merge like this - as they can with vector spaces. This point is beyond the assumption of Heisenbergs U.C princip. It is a feature of V.sp.

[Hythloday71]

@Hythloday71 - classically 2 observers can continually keep track of them, in QM, in an entangled state, the observers can no longer agree about the existence of the grn and red balls, there is a new combined vector state of 'green-blue' ball. In reality we do not consider properties to merge like this - as they can with vector spaces. This point is beyond the assumption of Heisenbergs U.C princip It is a feature of V.sp

[Hythloday71]

@Hythloday71 - The trouble with Physisists is they are practical men, they R usually of the shut up and calculate philosophy. I recently heard Gell-man speaking of the non-parradoxical nature of QM citing the classic eg of the guy wearing diff color socks, u see one, u know the color of the other - he said it like it was the end of the matter - but this is what Bells Ineq exactly speaks to the prohibition of that kind of thinking !

[csmcmillion]

Ugh - flog that cameraman!

[whois4tlas]

I don't get why at 1:11:35 he says that the result of the calculation is 1/4. I just keep getting 0. Can someone please explain?

[PLecN]

@whois4tlas Bit difficult to go through whole thing here. You've probably just missed out (or included) a minus sign somewhere.

[tw1ky]

@whois4tlas I'll try and explain although I guess is kind of hard in a comment, but here it goes: In the final multiplication you'll have 1/root2 (from the 'left' side, what he called the singlet), multliplying by another 1/root2 (that came from the 'right' side, ud,du over root2), multiplying for 1/2 (that was all that was left from the 'middle'). That is equal to 1/4. Please let me know if you got it or I'll try to explain better. Peace.

[MuggsMcGinnis]

What is the symbol he's drawing for 'projection operator'?

[waketherabble]

@MuggsMcGinnis Looks like a paragraph symbol.

[zeperf88]

Camera man zombie eats funny guy at 1:31. Ripe dorky brains!

[MuggsMcGinnis]

I wonder if some nice person in the audience has a good set of notes they could capture with a cam and post somewhere? I find that, if I'm not sure what he wrote, I can sometimes catch the writing in his shadow and pause.

[tcaruso2]

It seems like someone could cut the exposure on the board down with a video editing software package. Why doesn't someone do that because this lecture is essentially useless without seeing the whiteboards.

[apronin]

Susskind is great as usual! I was able to follow everything he said despite the terrible operator's work (indeed, it's often impossible to see what he is writing on the whiteboard).

[embeddedrf]

I think the problem with the video is that the operator has the exposure time of the camera set incorrectly!

Other than that it is a super great fantabulous lecture by Lenny Susskind talk show host!

[macgyver2210]

So...a highly intricate theoretical quantum/particle physics lecture....

...and you post it in 240p? Clearly Stanford's media arts department is horribly lacking.

[DaMav]

For some deeply frustrating reason the camera isn't picking up the board properly most of the time on this video -- so most of the time you can't read the board :-(

[shirankao69]

Those cell phones are annoying.

[bhigr]

Well, it started really boring, but this lecture is outstanding. I wish I could ge the lecture notes because I can't read the chalk board well. He has the habit of writing and erasing stuff almost simultaneously, which makes taking notes difficult.

[yasinal84]

To those whon cant see whats written on the board, here is a solution if you are using a laptop.

Look at your screen from a small angel and you will se whats written on the screen. It works perfectly for me.

[matharoofmaths]

the end was nice.

[manucapo]

and we must not only consider the practical use of it all, but also the aesthetic appeal of it, whats the practical use of a beautiful song or painting,

[pw3uk]

Technique & inspiration :-)

But I get your point.

[timcabc]

can't see what's written on the board, too bad

[TheZydor]

That in futures you can do this thinks on quantum computer.

[strapamotortoit]

who actualy watched it all?

[noobmartin]

I did, and I learnt a lot.

[strapamotortoit]

congratulations, now you know alot more about Quantum Entanglements. and that will help you how?

[noobmartin]

Well, since I'm a physics student, it does help me understand the world.

[strapamotortoit]

shut up noob

[random1221modnar]

i'm trying to watch it all, but how will this help you is actually a pretty good question. what good is knowledge without application?

[strapamotortoit]

EXACLY MY FRIEND!

how will the fact of knowing that particles travel in waves or something.

what will help is how to cook food without burning it and how to drive properly or not to spend your money on crap.

its all bollocks, they will all get boored of this crap some day and then realise they have wasted theyre life.

[TheZydor]

You should now that in fact the quantum entanglements can be future of quantum computers.

You uses a computer, did't you ?

[strapamotortoit]

a bit, internet use and phtotshop, a few pictures aswell, not as much as some people, your point is?

[Chronosaur]

So... what're you watching this on then? A cloud? A sheep? No, it's called a computer. Would we be able to build computers without semiconductor physics? Nope. And would we understand that without quantum mechanics? Nope. In fact the stuff semiconductor physics is based on is even more esoteric than this.

It's rare that this stuff gets used directly in engineering, but indirectly it underpins our quantitative understanding of, well, everything. The practical benifits of that should be obvious.

[strapamotortoit]

if you read my comment properly, i said that i do use computers. learn to read properly before you learn about Quantum Entanglements.

[jasonmathias]

Right on! Thanks Stanford. And thank you Mr. Leonard. I hope this goes deeper into the entanglement. So far this has been simple

[landin048]

I can't see what he's writing on that white board.

[RobertoGiorgi]

it stops 1.31

[andrmn]

There is bad video quality