Dissipation-Enabled Operator-Norm Locality Bounds for Bose-Hubbard Hamiltonians

Abstract: Closed bosonic lattice systems do not generally admit operator norm Lieb--Robinson bounds uniformly in the initial state. The reason is that the information propagation velocity can grow with the local boson occupancy, which can be macroscopically large. Here, we show that local dissipation restores an operator-norm Lieb--Robinson bound. We consider the dissipative Bose--Hubbard model described by a Lindbladian operator with on-site $\ell$-photon loss, $\ell>2$ and, for our main result, we establish an almost-ballistic Lieb-Robinson bound. Dissipation rapidly depletes highly occupied sites, thus regularizing the state on the Sobolev-type scale of local particle moments. The resulting moment bounds diverge as time approaches zero but remain integrable near zero at sufficiently low orders. We extend these ideas to treat cat-code dissipation and, for initial states in the code space, we prove a local adiabatic approximation uniform in the total volume. Further consequences include local channel approximation, a thermodynamic limit, and efficient digital quantum simulation. The point is that these applications are now available \textit{uniformly in the input state}, as for quantum spin systems, but in contrast to closed Bose--Hubbard systems.