Scientists at the Vienna University of Technology and the Okinawa Institute of Science and Technology (OIST) have demonstrated the first example of spontaneously emerging superradiant maser generation that does not require an external excitation source. In the experiment, quantum particles organized themselves to generate a stable and highly accurate microwave signal for an extended period-an effect once deemed impossible. The work is based on the phenomenon of superradiance, the collective emission of radiation by quantum particles. Under normal conditions, superradiance manifests as a brief and powerful burst: particles emit synchronously, reinforcing each other but quickly lose energy, causing the process to cease. It was thought that such collective effects inevitably damp down and cannot be sustained for long without external feedback. However, in the new experiment, the physicists found a different regime.
They linked a microwave resonant cavity with a dense ensemble of diamonds containing so-called NV centers-atomic defects where electron spins can be used as quantum states. These spins interacted with each other and with the common electromagnetic field inside the resonator. Initially, the system behaved as expected: a short superradiant pulse arose. But then scientists recorded something unexpected-a chain of narrow and long-lived microwave pulses that continued to appear spontaneously. The source of this effect was internal spin-spin interactions, which did not destroy quantum coherence but, on the contrary, constantly “restarted” the radiation.
Recent updates indicate that this groundbreaking research might pave the way for advanced microwave sources that could revolutionize quantum sensing technology. According to some theoretical physicists, self-sustaining microwave emissions could greatly enhance the precision of quantum sensors. These sensors, capable of detecting extremely weak changes in magnetic and electric fields, are invaluable in medical imaging, materials science, communication, and navigation systems. Notably, the quantum sensors market is projected to expand significantly by the end of the decade, driven by heightened demand for innovations in these applications.
Computer modeling showed that collective interactions between spins redistribute energy within the system and repopulate quantum levels, maintaining a stable generation regime. Thus, seemingly chaotic quantum interactions transformed into a mechanism of self-sustaining radiation-a fundamentally new type of collective quantum behavior. The authors emphasize that this discovery changes perceptions of the role of interactions in quantum systems. The same processes that usually impede and lead to the destruction of quantum states have, in this case, become the source of a coherent and extraordinarily ordered signal.
Given the ever-growing interest in quantum computing and quantum communication, these findings could further spur research expeditions into how macroscopic quantum effects could be harnessed for practical applications, perhaps even edging closer to fault-tolerant quantum computing.
