Completely Positive Map for Noisy Driven Quantum Systems Derived by Keldysh Expansion

Accurate modeling of decoherence errors in quan-tum processors is crucial for analyzing and improving gate fidelities. To increase the accuracy beyond that of the Lindblad dynamical map, several generalizations have been proposed, and the exploration of simpler and more systematic frameworks is still ongoing. In this paper, we introduce a decoherence model based on the Keldysh formalism. This formalism allows us to include non-periodic drives and correlated quantum noise in our model. In addition to its wide range of ap-plications, our method is also numerically simple, and yields a CPTP map. These features allow us to inte-grate the Keldysh map with quantum-optimal-control techniques. We demonstrate that this strategy gener-ates pulses that mitigate correlated quantum noise in qubit state-transfer and gate operations.