The question of whether gravity is a quantum phenomenon has long puzzled physicists, and researchers are now working on experimental approaches to test it. Dongchel Shin, a PhD candidate at MIT’s Mechanical Engineering Department, has recently made progress in this area by demonstrating laser cooling of a centimeter-long torsional oscillator.
Torsion pendulums have been used since 1798 to measure Newton’s gravitational constant and study gravity’s behavior. However, researchers are now using advanced techniques like laser cooling to explore the quantum aspects of gravity. Shin’s team has successfully cooled a centimeter-scale torsional oscillator from room temperature to 10 millikelvins, nearly 100 times cooler than previous systems.
The approach used involves shining a laser onto the oscillator and using a mirrored optical lever to cancel out unwanted jitter caused by air currents or vibrations. This technique allowed the researchers to detect motion with extreme precision, nearly 10 times better than the oscillator’s own quantum zero-point fluctuations.
Shin believes this work is just the beginning, as he aims to further strengthen the optical interaction to reach the actual quantum ground state. By achieving this, the team can test whether gravity needs to be described by a quantum theory. The collaboration involved multiple departments and researchers from MIT and the University of Utah.
The challenge in studying quantum aspects of gravity lies not only in physics but also in system design, nanofabrication, optics, control, and electronics. Shin’s background in mechanical engineering has been instrumental in navigating these diverse domains, allowing him to contribute meaningfully across multiple disciplines.
Source: https://news.mit.edu/2025/is-gravity-quantum-0520