Fig. 3.

Indirect coupling between separated resonators via a phonon cavity. a Raman-like coupling between modes R₁ and R₃ via virtual excitation of the phonon cavity R₂. The coupling strength can be controlled by changing the detuning Δ₁₂. b Effective coupling as a function of Δ₁₂. The error bars are obtained from the s. e. m. of the measured data and are extracted from the statistical deviation of the estimated values at different detunings from Supplementary Fig. 7. The red line is given by Ω₁₃ = Ω₁₂Ω₂₃/2Δ₁₂, with Ω₁₂/2π = 240 kHz and Ω₂₃/2π = 170 kHz