Quantum Fisher information of two superconducting charge qubits under dephasing noisy channel

The Quantum Fisher information (QFI) of a two-charged qubits system that interacts locally with a dephasing channel is quantified with respect to the charged qubits’ and the channel’s parameters. The behavior of Fisher's information displays different phenomena, such as the sudden changes (increasing/decreasing), the gradual decay, and the freezing of the QFI. It is shown that the QFI of the dephasing parameter decays gradually and vanishes completely as one increases the initial energies of the qubits and their mutual energy. The possibility of estimating the charged qubits’ energies may be maximized at smaller values of the initial dephasing parameter. The estimation degree of the mutual information reaches its upper bounds by increasing the initial energies. It is depicted that, by controlling the qubits’ and the channel’s parameters, the QFI may be frozen. We expect this result to be interesting in the context of quantum encoding and cryptography.