Researchers built a solid-state superradiant maser that generates and maintains macroscopic quantum coherence under ambient conditions. Large-scale quantum coherence in solid materials normally collapses unless cooled to very low temperatures or triggered in brief pulses. The device overcomes this limit as diamond defect spins lock their magnetic oscillations with microwave photons trapped inside a cavity.
Roughly one hundred trillion nitrogen-vacancy defect spins in the diamond build up collective energy alongside one billion trapped microwave photons. These spins emit radiation that bounces between the cavity walls, acting like physical metronomes that pull each other into a shared rhythm. The resonant microwave field forces the entire population of spins to oscillate in lockstep instead of radiating independently. Tuning the operating settings shifts the emission between steady continuous waves, synchronized time-crystal modulations, and rapid superradiant bursts.
The researchers tested the setup by coupling a diamond crystal containing nitrogen-vacancy centers to a microwave cavity under ambient room conditions. They recorded sustained coherence across approximately ten to the fourteenth spins and ten to the ninth microwave photons. By varying system parameters across threshold regimes, they observed fixed-frequency spin synchronization, a coherent time crystal of large spins, and unsynchronized transient pulses.
The researchers state that macroscopic quantum coherence can be spontaneously generated and sustained inside solid materials at room temperature. This demonstration provides a solid-state platform for exploring bright quantum light and many-body correlations without cryogenic systems.