A protocol to estimate the average fidelity of the bipartite system

In present work, we shall develope a protocol to estimate the average fidelity for the bipartite system. We show that the average fidelity should be known if the three measurable quantities, the average survive probability of the product state and the the average survive probablity of each subsystem, have been decided. Our protocol can be also applied to decide the selected element of the quantum proess matrix.