We present direct and deterministic entanglement of two macroscopic mechanical elements (drums) for the first time. We show strong correlations between the position of one drum and the position of another drum with a corresponding anti-correlation for the momenta. Proving entanglement requires measuring the variances of the correlated signals with a resolution and an accuracy that are well below the zero-temperature quantum fluctuations of the drums. The amount of measured correlations (inferred) is more than a factor of two better than the best correlations that can be achieved classically. The amount of entanglement measured and the ability to directly observe it without noise subtraction encourages future research directions that include: entanglement distribution between separate dilution refrigerators, quantum illumination of objects, and quantum teleportation of mechanical states. 

Reference: Kotler et. al. Science 372, 622-625 (2021)