Entanglement of macroscopic objects

Generation and characterization of non-classical states has been moving forward thanks to a continued effort to
control the environment (dissipation), increase the interaction (coupling) and measure carefully (measurement
efficiency). While we discuss all three, this talk will focus on the latter. Specifically for microwave-based
platforms, improving measurement efficiency has been an outstanding challenge for superconducting qubits and
mechanics both for detection and feedback control.
Our system of choice is made of mechanical elements of ~10 micrometer size that interface a microwave resonator
for detection and manipulation. 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-point fluctuations
of the drums. The correlated signal variance (inferred) is more than a factor of two smaller than the zero-point
motion induced fluctuations of any classical state. Moreover, these correlations survive ~70% of microwave loss
while retaining non-classicality.
The amount of entanglement measured encourages future research directions that include: entanglement
distribution between separate dilution refrigerators, quantum illumination of objects, and quantum teleportation of
mechanical states.