Figure 1

Sketch of the setup: A BEC in a box-like potential that acts as a cavity for the phononic excitations. Two phononic modes m and n are initially prepared in a thermal two-mode squeezed state represented by the initial covariance matrix \(\sigma_{0}\). A gravitational wave of amplitude ϵ transforms the state producing excitations. The new state \(\sigma_{\epsilon}\) depends on ϵ. Measurements on the modes can be used to estimate the amplitude of the spacetime distortion.