One-milligram torsional pendulum toward experiments at the quantum-gravity interface

Understand

Probing the possibility of entanglement generation through gravity offers a path to tackle the question of whether gravitational fields possess a quantum mechanical nature.

• A potential realization necessitates systems with low-frequency dynamics at an optimal mass scale, for which the microgram-to-milligram range is a strong contender.
• Here, after refining a figure-of-merit for the problem, we present a 1-milligram torsional pendulum operating at 18 Hz.
• We demonstrate laser cooling its motion from room temperature to 240~microkelvins, surpassing by over 20-fold the coldest motions attained for oscillators ranging from micrograms to kilograms.