Robustness of multipartite entangled states in passive PT -symmetric qubits

Non-Hermitian quantum systems have attracted significant interest in recent years due to the presence of unique spectral singularities in which eigenvalues and eigenvectors coalesce. Those singularities are known as exceptional points (EPs). The drastic changes of the non-Hermitian systems around their EPs have led to unique entanglement dynamics, which remained elusive until quite recently. In this work, we theoretically investigate the robustness of multipartite entanglement induced by EPs of the passive PT-symmetric non-Hermitian superconducting qubits, both in stand-alone configurations and hybrid setups with Hermitian qubits. In particular, we consider the qubits with both all-to-all and nearest-neighbor couplings under uniform and nonuniform coupling strengths. Our results reveal that non-Hermitian qubits with all-to-all coupling generate GHZ states, while those with nearest-neighbor interactions produce W states. These entangled states are resilient to nonuniform couplings, off-resonant driving fields, and decoherence effects. Moreover, the hybrid configurations combining Hermitian and non-Hermitian qubits indicate the necessity of EPs for rapidly generating and maintaining genuine multipartite entanglement. Additionally, driving the PT-symmetric qubits with a strong Rabi frequency can help sustain the entanglement over time by countering losses, while strong interqubit coupling favors the entangled states in the low dissipation regime. We also demonstrate that increasing the number of non-Hermitian qubits speeds up multipartite entanglement generation due to enhanced collective interactions. These findings reveal that exploiting non-Hermitian systems and their associated EPs is beneficial for generating robust and genuine entangled states which are useful for both fundamental studies and quantum technologies.