Quantum freezing at room temperature locks nanoparticle at 92% purity

Scientists have achieved a significant breakthrough by freezing the rotational motion of a tiny glass nanoparticle at room temperature to a record quantum purity of 92%. This nanoparticle, though still extremely small, is much larger than typical quantum-scale objects and remains hot internally at several hundred degrees Celsius. Traditionally, observing quantum behavior in larger objects required cooling them near absolute zero and isolating them in vacuum to prevent environmental interference. However, this study bypasses those constraints by focusing solely on the particle’s rotational motion rather than its entire internal energy, enabling quantum ground-state cooling without massive cryogenic setups. The researchers used a slightly elliptical nanoparticle trapped in an electromagnetic field, where it naturally wobbles like a compass needle. By precisely controlling laser light within a high-finesse optical cavity and adjusting mirrors to favor energy removal over addition, they drained nearly all rotational energy, achieving about 0.04 quanta of residual energy. This delicate process also involved managing quantum noise from the lasers to maintain the purity of the