Absorbing state phase transitions beyond directed percolation in dissipative quantum state preparation

We show that absorbing state phase transitions where the absorbing state itself exhibits long-range phase coherence can lead to critical behavior distinct from directed percolation. To do this, we investigate a simple, purely dissipative quantum reaction-diffusion model, which may also be viewed as a dissipative quantum state preparation procedure for the (generalized) W state with errors. The "error" Lindblad jump operators preserve the W state as a dark state, but nonetheless act to decohere the system and induce the phase transition. We find cases where the preparation protocol is either fragile or robust against weak error quantum jump rates and show that local remnants of the coherence persist in the decohering phase. The distinct critical behavior stems from the spreading of coherence throughout the system at the critical point.