  We theoretically proposed one of the approaches achieving the quantum
entanglement between light and microwave by means of electro-optic effect.
Based on the established full quantum model of electro-optic interaction, the
entanglement characteristics between light and microwave are studied by using
the logarithmic negativity as a measure of the steady-state equilibrium
operating point of the system. The investigation shows that the entanglement
between light and microwave is a complicated function of multiple physical
parameters, the parameters such as ambient temperature, optical detuning,
microwave detuning and coupling coefficient have an important influence on the
entanglement. When the system operates at narrow pulse widths and/or low
repetition frequencies, it has obvious entanglement about 20 K, which is robust
to the thermal environment.
