  We investigate theoretically the model of two \qubits" system (one qubit
having an auxiliary level) interacting with a single-mode resonator in the
ultrastrong coupling regime. We show that a single photon could simultaneously
excite two qubits without breaking the parity symmetry of system by properly
encoding the excited states of qubits. The optimal parameter regime for
achieving high probability approaching one is identified in the case of
ignoring the system dissipation. Moreover, using experimentally feasible
parameters, we also analyze the dissipation dynamics of the system, and present
the realization of two-qubit excitation induced by single-photon. This work
offers an alternative approach to realize the single-photon-induced two qubits
excitation, which should advance the development of single-photon quantum
technologies and have potential applications in quantum information science.
