Researchers cool a 40 kg object to near its quantum ground state - Ars Technica

Objects that obey the rules of quantum mechanics behave very differently from those in the familiar world around us.

Still, there has been progress in increasing the size of the objects we can place in a quantum state, with small oscillators and even grains of sand being notable examples.

But in today's issue of Science, researchers report that they've gotten close to putting a big object into its quantum ground state—a really big object: the 40 kilogram mirrors of the gravitational-wave observatory known as LIGO.

Finally, a damping system reads the position of the mirror and exerts force in order to keep it in its intended location.

This allows control voltages to impart a force to the mirror.

Measurements of the location and motion of the mirror are processed and compensatory forces calculated, and the appropriate signals are generated to apply that force via the electrical system.

At the end of the process, there were likely 11 phonons in the 40 kilogram mirror.

That's not the quantum ground state, which would involve emptying the system of phonons.

The new work, they suggest, "hints at the tantalizing prospect of studying gravitational decoherence on massive quantum systems." And, compared to a grain of sand, 40 kg certainly qualifies as massive.