Robust Self-Testing of Four-Qubit Symmetric States

Quantum verification has been highlighted as a significant challenge on the road to scalable technology, especially with the rapid development of quantum computing. To verify quantum states, self-testing is proposed as a device-independent concept, which is based only on the observed statistics. Previous studies focused on bipartite states and some multipartite states, including all symmetric states, but only in the case of three qubits. In this paper, we first give a criterion for the self-testing of a four-qubit symmetric state with a special structure and the robustness analysis based on vector norm inequalities. Then we generalize the idea to a family of parameterized four-qubit symmetric states through projections onto two subsystems.

Automated summary

In this paper, a method for self-testing four-qubit symmetric states is proposed, and the robustness analysis is conducted based on vector norm inequalities. The authors generalize this idea to a parameterized family of four-qubit symmetric states.