As in the case of a single qubit, the probability of measuring a particular computational basis state | x ⟩ ⟩ is the square of the modulus of its amplitude, or associated coefficient, | α α x | 2 , subject to the normalization condition ∑ ∑ x ∈ ∈ 0 , 1 | α α x | 2 = 1 . The normalization condition guarantees that the sum of the probabilities add up to 1, meaning that upon measurement, one of the states will be observed.