Decoherence errors, caused by the interaction of quantum systems with their environment, pose a major challenge for the practical implementation of quantum computing. Accurately modeling these errors is essential for analyzing and improving gate fidelities. While Lindblad master equation and its several generalizations have been proposed, there is still ongoing exploration for simpler and more systematic frameworks. In this paper, we introduce a novel decoherence model based on the Keldysh formalism that addresses the limitations of previous methods. The Keldysh map provides a rigorous derivation for handling non-periodic drives and correlated quantum noise, resulting in a numerically simple, completely positive and trace-preserving (CPTP) map. By integrating the Keldysh map with quantum-optimal-control techniques, we demonstrate how this model generates pulses that mitigate correlated quantum noise in qubit state-transfer and gate operations. The results of our study hold great promise for advancing the practical implementation of quantum computing systems.

The paper can be found here.