  We obtain a generalisation of the Quantum Unique Ergodicity for holomorphic
cusp forms on $\mathrm{SL}_2(\mathbb{Z}) \backslash \mathbb{H}$ in the weight
aspect. We show that correlations of masses coming from off-diagonal terms
dissipate as the weight tends to infinity. This corresponds to classifying the
possible quantum limits along any sequence of Hecke eigenforms of increasing
weight. Our new ingredient is to incorporate the spectral theory of weight $k$
automorphic functions to the method of Holowinsky-Soundararajan. For
Holowinsky's shifted convolution sums approach, we need to develop new bounds
for the Fourier coefficients of weight $k$ cusp forms. For Soundararajan's
subconvexity approach, we use Ichino's formula for evaluating triple product
integrals.
