# I Quantum Entanglement-Susskind-lecture 4&5

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1. Aug 15, 2016

### say_cheese

In Lecture 5 on quantum entanglement, Susskind calculates the Bell's inequality terms using projection operator (a difficult concept and a tedious derivation). However, I believe the following

I obtained the result on the Bell's inequality using the probability of spin of an electron prepared with spin in n direction, being up in direction m (Lecture 4): (1+cos(tmn))/2

A not B on a singlet for the case of A being up and B not being 45 deg is then given by

for |u d>= 1. (1+/- 1/√2)/2 For the case in lecture 5, it is the - sign
similarly
for |d u> =0. (1- +1/√2)/2

Gives the same answer with a simpler way.

The cosine dependence also is much more comprehensive in explaining the explanation in
https://en.wikipedia.org/wiki/Bell's_theorem

2. Aug 21, 2016

### Greg Bernhardt

Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.