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Accepted

### For a Nqbit, prove that $\langle|\alpha_i|^2\rangle=1/2^N$ and that $\langle|\alpha_i \alpha_j|^2\rangle= 2^{\delta_{ij}-N}/(1+2^N)$

The claim certainly works for a single qubit. Here, you should think of $$\alpha_0=\cos\frac{\theta}{2},\qquad \alpha_1=\sin\frac{\theta}{2}e^{i\phi}.$$ So, you can readily calculate, for example, ...
• 60.2k

• 2,833
Accepted

### Why do Bell states have all real coefficients?

I would call $|\psi\rangle = \frac{1}{\sqrt 2} (|00\rangle + i|11\rangle)$ also a Bell state due to the properties that you have already listed. There is nothing really special of $|\Phi^+\rangle$ ...
• 858
Accepted

### Relative entropy of entanglement

I'm afraid being separable doesn't help with computing the logarithm. Having the form you mentioned does make the optimization easier, as it makes it a separable spectral function, but it's not ...
• 2,833
1 vote
Accepted

### CHSH game sharing a general state

Having the players share additional EPR pairs will not increase the probability of winning the game. This is because the Tsirelson bound of $2\sqrt{2}$ is the optimal value for the CHSH game amongst ...
• 2,111

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