  We propose to realize the two-mode continuous-variable entanglement of
microwave photons in an electro-optic system, consisting of two superconducting
microwave resonators and one or two optical cavities filled with certain
electro-optic medium. The cascaded and parallel schemes realize such
entanglement via coherent control on the dynamics of the system, while the
dissipative dynamical scheme utilizes the reservoir-engineering approach and
exploits the optical dissipation as a useful resource. We show that, for all
the schemes, the amount of entanglement is determined by the ratio of the
effective coupling strengths of "beam-splitter" and "two-mode squeezing"
interactions, rather than their amplitudes.
