Two-Stage Solution for Ancilla-Assisted Quantum Process Tomography: Error Analysis and Optimal Design

Shuixin Xiao, Yuanlong Wang, Daoyi Dong, Jun Zhang

Abstract: Quantum process tomography (QPT) is a fundamental task to characterize the dynamics of quantum systems. In contrast to standard QPT, ancilla-assisted process tomography (AAPT) framework introduces an extra ancilla system such that a single input state is needed. In this paper, we extend the two-stage solution, a method originally designed for standard QPT, to perform AAPT. Our algorithm has $O(Md_{A}^{2}d_{B}^{2})$ computational complexity where $M$ is the type number of the measurement operators, $d_{A}$ is the dimension of the quantum system of interest, and $d_{B}$ is the dimension of the ancilla system. Then we establish an error upper bound and further discuss the optimal design on the input state in AAPT. A numerical example on a phase damping process demonstrates the effectiveness of the optimal design and illustrates the theoretical error analysis.

External IDs:dblp:conf/cdc/Xiao0DZ23