Quantifying Quantum Information Processes
Jen-Hsiang Hsieh1*, Shih-Hsuan Chen1, Che-Ming Li1
1Department of Engineering Science, National Cheng Kung University, Tainan City, Taiwan
* presenting author:Jen Hsiang Hsieh, email:joseph20307@gmail.com
Quantum information processing, such as quantum computation and quantum communication, outperforms the conventional approach with classical information theory. However, there exists no perfect quantum information process in practice due to unexpected environmental interference and imperfect experimental conditions, which makes quantifying quantum processes for information tasks critically necessary for evaluating the reliability of a practical information process. Here, we introduce a method to quantify the robustness against noise, i.e. the minimum amount of noise such that quantum processes remain quantum properties. We also propose criteria on quantum process fidelity between an experimental process and a target quantum process to rule out any classical mimicries, which can be used to evaluate the reliability of a practical information process. For quantum computation, we verify that perfect one-qubit logical gates possess the maximum robustness. Moreover, it can be extended to the cases of multi-qubit logical gates. For qubit transmission, we consider how the robustness changes with the noise intensity in different noisy channels and found that the robustness is more sensitive to depolarizing channel than amplitude damping and phase damping channels. Finally, using our indicator of the reliability, we can obtain the minimum concurrence of entangled states needed to perform the teleportation of one entangled qubit pair.

Keywords: Quantum information, robustness