Controllable non-Hermitian qubit-qubit Coupling in Superconducting quantum Circuit

Abstract: We propose a theoretical scheme to realize the controllable non-Hermitian qubit-qubit coupling by adding a high-loss resonator in tunable coupling superconducting quantum circuit. By changing the effective qubit-qubit coupling, phase and amplitude of resonator-qubit interaction, and the qubits' quantum states, we can continually tune the energy level attraction, position of EP (exceptional point), and the nonreciprocity in the non-Hermitian superconducting circuit. The EPs and non-reciprocity can affect the quantum states' evolutions and exchange efficiencies for two qubits in the non-Hermitian superconducting circuit. The controllable non-Hermitian and nonreciprocal interactions between two qubits provide a new insights and methods for exploring the unconventional quantum effects in superconducting quantum circuit.