Quantum Emulation of Gravitational Waves
  Gravitational waves, as predicted by Einstein's general relativity theory, appear as ripples in the fabric of spacetime traveling at the speed of light. We prove that the propagation of small amplitude gravitational waves in a curved spacetime is equivalent to the propagation of a subspace of electromagnetic states. We use this result to propose the use of entangled photons to emulate the evolution of gravitational waves in curved spacetimes by means of experimental electromagnetic setups featuring metamaterials. 
Ivan Fernandez-Corbaton, Mauro Cirio, Alexander B\"use, Lucas Lamata,   Enrique Solano and Gabriel Molina-Terriza
quant-ph cond-mat.mes-hall cond-mat.supr-con gr-qc physics.optics