Optimal Joint Measurements of Qubit Observables

In quantum mechanics, two incompatible sharp observables A and B can nevertheless be simultaneously approximated by noisy measurements and at the expense of tolerating some inaccuracy. By quantifying this inaccuracy using a measure of error, we want to find the pair C, D that most accurately approximates A, B under the constraint of joint measurability, and in doing so characterize the lower bound of the admissible region of error pairs spanned by all pairs of compatible approximators.
This Demonstration will find optimal approximators and the lower bound of the admissible region for the case of two sharp qubit observables.