Bad Qubits — Learn Quantum by Doing

Multiple choice

For the Bell state |Phi+>, the correlation in the X-Z plane is E(theta_a, theta_b) = cos(theta_a - theta_b). With a=0, a'=pi/2, b=pi/4, b'=-pi/4, evaluate the CHSH quantity S = E(a,b) + E(a,b') + E(a',b) - E(a',b'). What is |S|?

2*sqrt(2) ≈ 2.828
sqrt(2) ≈ 1.414
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