  The dynamics of a charged two-qubit system prepared initially in a maximum
entangled state is discussed, where each qubit interacts independently with a
dephasing channel. The Fisher information is used to estimate the channel and
the energy parameters. Moreover, the contribution from different parts of
Fisher information is discussed. We show that, the degree of estimation of any
parameter depends on the initial value of this parameter. It turns out that the
upper bounds of Fisher information with respect to the dephasing parameter
increase and that corresponding to coupling parameter decreases as the initial
energy of each qubit increases.
