Entanglement of macroscopic objects

Observing quantum phenomena at the macroscopic scale has captured both the attention of scientists and the imagination of the public for more than a century. Although quantum mechanics presumably applies to objects of all sizes, directly observing entanglement becomes harder as masses increase, requiring measurement and control with a vanishingly small error. Here we strongly and deterministically entangle two massive mechanical oscillators (~ 70 pg) and directly observe their state. Our technology allows for on-demand reproducible entanglement generation. For direct state observation, we implement a near quantum-limited measurement of the positions and momenta of both mechanical oscillators in every realization of the experiment. By repeating these measurements, we completely characterize their joint covariance matrix. This tomography demonstrates clear evidence of continuous variables (CV) entanglement in the measurement signals, without noise subtraction.

The amount of entanglement measured and the ability to directly ovserve 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.