Spin behavior in entangled electron pair

In summary, the quoted conversation discusses the concept of entangled electron pairs and how measuring the spin of one electron can affect the spin of the other. The statement also clarifies that the measurement of spin is not truly random, but rather forces the electron to have a specific spin in that direction while eliminating any tendency for it to have a particular spin in other directions. The initial statement is correct in that the spin of entangled electrons can be opposite, but it is not known which will be up and which will be down until measured. The speaker suggests reading EPR paradox and Bell's theorem for further understanding.
  • #1
daezy
7
0
Isn't it that in entangled electron pair, it's random which side will have
up and down spin... the two sides should produce opposite spin but the order is
random.. however I'm confused by the following statements:

"Recall that when you measure an electron's spin in one direction you
erase all information about the electron's spin in any other
direction. By this I mean the following: If I measure the spin in the
left/right direction I will always find it pointing exactly left or
exactly right. Say I measure it pointing left. If I measure it again
in the left/right direction then I will definitely see it pointing
left again. If I measure it in the up/down direction, however, then I
will have 50/50 odds of seeing it point either way. Once I do that
measurement, however, I will have fixed it to be pointing either up or
down, and a left/right measurement will once again yield 50/50 odds".


What is the above talking about? By using say up detector. You can
bias the pair to *always* produce up spin in that detector? But I
thought it's supposed to be random. Hope someone can clarify.
 
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  • #2
The quoted statement is about a single electron only, not an entangled pair. The statement does apply to one electron in an entangled pair as well. For that one electron, if you measure it's spin about a particular axis, say "x" then you force it's spin about x to be up or down AND you eliminate any tendency for the electron to have a particular spin about y or z. This means a subsequent measurement of the spin about x will give the same result as the last, but a subsequent measurement on the spin about y or z will have a 50/50 chance of being up or down.

Your initial statement is also correct, if the spin of 2 electrons is entangled so that the net spin about x is 0 then the first time you measure their spin about x you will get opposite measurements on the 2 electrons (one up one down) but you do not know which will be up and which will be down until you measure.
 
  • #3
I just humbly ask daezy to read the EPR pardox and the one which follows after it- Bell's theorem.In detail(my instructor saw and said so).
 

1. What is entanglement in electron pairs?

Entanglement in electron pairs is a quantum phenomenon where two or more electrons become correlated in a way that their properties are dependent on each other, regardless of the distance between them.

2. How does spin behavior affect entangled electron pairs?

Spin behavior in entangled electron pairs is closely related to the entanglement itself. The spin of an electron refers to its intrinsic angular momentum, and it can be either "up" or "down". In an entangled pair, the spin of one electron affects the spin of the other, even when they are separated by a large distance.

3. Can entangled electron pairs have opposite spin orientations?

Yes, entangled electron pairs can have opposite spin orientations. This is known as spin anti-correlation and is a common feature of entangled systems. In this case, if one electron has an "up" spin, the other will have a "down" spin.

4. How is the spin behavior of entangled electron pairs measured?

The spin behavior of entangled electron pairs can be measured using various techniques, such as Bell inequality measurements or spin correlation measurements. These techniques involve measuring the correlation between the spins of the two entangled electrons and comparing it to theoretical predictions.

5. What are the potential applications of entangled electron pairs and their spin behavior?

Entangled electron pairs and their spin behavior have potential applications in quantum computing, quantum cryptography, and quantum communication. They can also be used to study the fundamental principles of quantum mechanics and to test the limits of our current understanding of the universe.

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