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In this paper, a protocol for nondestructive parity meter (NPM) of two cat‐state qubits is proposed. The physical model contains two cavities and an auxiliary qubit. For each cavity, the quantum information is encoded on the odd and even cat state, forming a cat‐state qubit. By adjusting the strength of the driving field on the auxiliary qubit, an effective Hamiltonian for cavity‐selective transition is derived. Moreover, reverse engineering based on the effective Hamiltonian is applied to find the evolution path, and the systematic‐error‐sensitivity nullification method is used to select proper parameters of the evolution path. In this way, robust control fields are designed to combat the influence of the systematic errors. Furthermore, the effects of random noise and decoherence on the fidelity of the protocol are considered. Numerical simulations show that the protocol is insensitive to the experimental imperfection, including systematic errors, random noise and decoherence. Therefore, the protocol is expected to expand the vision of realizing NPM. [ABSTRACT FROM AUTHOR]

Parity meter is the core step of many quantum information works. In this paper, a robust and accurate protocol to construct a parity meter of two artificial atoms coupled to a cavity is proposed. Specifically, when the atomic system is in states with different parities, the cavity will evolve into different states. Then, the parity information of the atomic system can be distinguished by measuring the state of the cavity via the homodyne measurement. In addition, the influence of decoherence (including the cavity decay, the atomic spontaneous emission, and the dephasing) and systematic errors are numerically discussed. The results show that the protocol is robust against these negative factors. Therefore, this protocol may provide helpful perspectives for accurate parity meters. [ABSTRACT FROM AUTHOR]