Bell's Theorem - Bell Inequality

Classical computing:

For binary bits measurements: 

a0b0 + a0b1 + a1b0 - a1b1 <=2

In quantum mechanics 

For using qubits, it can violate the the inequlity:

At Bell state / entanglement 

The average of four measures can be over 2 sqrt(2) = 2.828..., exceed two! This can be proofed in the lab setting:

Experiment to show the violation of Bell Inequality