Quantum particles can collectively produce signals that are stronger than those generated by a single particle, a phenomenon known as superradiance. Historically, superradiance has been associated with rapid energy loss in quantum systems, posing challenges for quantum technologies. A new study, published in Nature Physics, presents findings that collective superradiant effects can instead generate self-sustained, long-lived microwave signals, offering potential for future quantum devices.
Dr. Wenzel Kersten, the study's first author, stated that interactions between spins can drive this emission, with the system organizing itself to produce a coherent microwave signal despite conditions typically associated with disruption. Researchers from TU Wien (Vienna University of Technology) and the Okinawa Institute of Science and Technology (OIST) have demonstrated self-induced superradiant masing, which involves spontaneous, long-lived bursts of microwave emission generated without external driving. This discovery provides a new method for generating stable and precise microwave signals.
Collective Behavior and Signal Generation
To investigate collective behavior in spin systems, the researchers coupled a dense ensemble of nitrogen-vacancy (NV) centers in diamond—atomic defects hosting electron spins that function as small magnets—to a microwave cavity.
Professor William Munro, a co-author and head of OIST's Quantum Engineering and Design Unit, reported the observation of an initial superradiant burst, followed by a series of narrow, long-lived microwave pulses. Through large-scale computational simulations, the team identified the source of this pulsing as self-induced spin interactions that dynamically repopulate energy levels, sustaining the emission without external pumping. This indicates that the system operates autonomously, with spin-spin interactions continually triggering new transitions and revealing a new mode of collective quantum behavior.
Potential Applications
These findings suggest practical applications. The development of stable, self-sustained microwave emission could contribute to technologies such as precise clocks, communication links, and navigation systems. These technologies underpin global infrastructure, including GPS, telecommunications, radar, and satellite networks.
Professor Jörg Schmiedmayer of the Vienna Center for Quantum Science and Technology, TU Wien, noted that the principles observed could also enhance quantum sensors. These sensors are capable of detecting small changes in magnetic or electric fields, potentially benefiting fields like medical imaging, materials science, and environmental monitoring. The research demonstrates how insights into quantum behavior can lead to the development of new tools and technologies for future scientific and industrial applications.