Exact Correlation Functions for Dual-Unitary Lattice Models in 1+1 Dimensions

We consider a class of quantum lattice models in 1+1 dimensions represented as local quantum circuits that enjoy a particular dual-unitarity property. In essence, this property ensures that both the evolution in time and that in space are given in terms of unitary transfer matrices. We show that for this class of circuits, generically nonintegrable, one can compute explicitly all dynamical correlations of local observables. Our result is exact, nonpertubative, and holds for any dimension d of the local Hilbert space. In the minimal case of qubits (d=2) we also present a classification of all dual-unitary circuits which allows us to single out a number of distinct classes for the behavior of the dynamical correlations. We find noninteracting classes, where all correlations are preserved, the ergodic and mixing one, where all correlations decay, and, interestingly, also classes that are both interacting and nonergodic.