A 1-milligram rotor’s motion is controlled with quantum measurement

The team achieved this by isolating the rotor and resolving thermal fluctuations with a damping rate of only 7 nHz, enabling continuous quantum measurement of its motion. This control allows for conditional states with entropic temperatures as low as 140 nK, two orders of magnitude colder than previously achieved in similar experiments, and opens new avenues for testing modifications of quantum mechanics and probing the quantum-classical interface. This exceptionally low damping rate signifies a substantial reduction in external disturbances affecting the rotor’s motion, allowing for the observation of subtle quantum effects previously masked by noise. Researchers realized this isolation within a suspended rotor operating in a free-particle regime, a configuration that supports advancing quantum sensing and fundamental tests of physics. Continuous quantum measurement of the rotor localizes its motion, generating conditional states with entropic temperatures reaching 140 nK, a value significantly lower than previously attainable in tabletop optomechanical experiments. This temperature represents a quantitative measure of the control achieved over the free-particle demonstrating a performance improvement of two orders of magnitude over existing methods. The technique relies on tracking the rotor’s yaw…