Open-quantum-system simulation through exploiting noise on quantum computers

We present a general framework for simulating open quantum systems by exploiting the device noise. We find that pseudo-identity unitary transformations on system qubits in the presence of noise can generate nontrivial quantum channels driving open-system dynamics. Controlling parameters in these transformations allows us to simulate selective state-to-state transitions as well as the long-lived coherences found in systems such as photosynthetic light-harvesting complexes. These results suggest a general framework in which parameters in pseudo-identity unitary transformations can be chosen to generate arbitrary nonunitary system-bath channels without any additional qubits representing bath dynamics. The demonstrated controllability of the bath through these transformations establishes different possibilities for the efficient simulation of open quantum systems on quantum devices.