Two-stage solution of quantum process tomography in the natural basis

Quantum process tomography (QPT) is a critical task for characterizing the dynamics of quantum systems and achieving precise quantum control. In this paper, we propose an effective two-stage solution (TSS) for QPT in the natural basis. Our algorithm has O(d(6)) computational complexity where d is the dimension of the quantum system. We establish an error bound O(d(5/)root N) where N is the copy number for each output state. The numerical examples compared with a convex optimization algorithm demonstrate the effectiveness of our algorithm.