Answer: To construct an MPO (Matrix Product Operator) that contrasts how the Dursleys treated Dudley and Harry, we first need to define the operators that will be used to describe the behavior of the Dursleys towards each of the two boys.
Let's represent the Dursleys' treatment of Dudley as "favorable" and the Dursleys' treatment of Harry as "unfavorable." We can then define the following operators:
$F$: represents the favorable treatment that Dudley receives from the Dursleys.
$U$: represents the unfavorable treatment that Harry receives from the Dursleys.
With these operators in mind, we can now construct an MPO that contrasts the Dursleys' treatment of Dudley and Harry as follows:
$M = \sum_{i,j,k,l} F_{i,j} \otimes U_{j,k} \otimes I_{k,l}$
In this MPO, the operator $F$ acts on the first tensor site, the operator $U$ acts on the second tensor site, and the identity operator $I$ acts on the third tensor site. The contraction of this MPO will result in a matrix that contrasts the Dursleys' treatment of Dudley and Harry. The diagonal elements of the resulting matrix will represent the degree of favorability or unfavorability towards each boy, while the off-diagonal elements will represent the contrast between the two.
Note that the specific form of the operators $F$ and $U$ will depend on the particular aspects of the Dursleys' treatment of Dudley and Harry that are being contrasted. For example, if we focus on how the Dursleys treated each boy at meal times, we could define $F$ to represent the amount and quality of food that Dudley received, while $U$ could represent the small portions and poor quality of food that Harry received. Alternatively, if we focus on how the Dursleys treated each boy in terms of love and affection, we could define $F$ to represent the attention and affection that Dudley received, while $U$ could represent the neglect and abuse that Harry experienced.