(a) Schematic of a three-mode circuit electromechanical system in which two mechanical oscillators are coupled to a single microwave cavity denoted by equivalent inductance L and equivalent capacitance C. The mechanical displacements x₁ and x₂ independently modulate the total capacitance C, and hence, the cavity frequency ω_c. A strong pump field at the frequency ω_pu and a weak probe field at the frequency are applied to the microwave cavity simultaneously. (b) Level diagram of the hybrid system when the pump field is red detuned by an amount ω_m = (ω₁ + ω₂)/2.