Researchers at Cornell and MIT have demonstrated how noisy, amplified lasers can be transformed into ultra-stable beams. According to the researchers, the method will expand photonic technologies that rely on both high power and high precision. “What was super surprising is that the noise is so low that there's no classical laser beam that has those same properties,” said Nicholas Rivera, assistant professor of applied and engineering physics at Cornell Engineering, who co-led the study with Shiekh Uddin, postdoctoral associate at MIT. “It's in a quantum state that has no classical analog.” Such quantum light is typically produced using nonamplified, low-power lasers in controlled settings. The current research showed that amplified light with high noise can be transformed into an “intensity-squeezed” state of light, in which the fluctuations in the number of photons are reduced below a fundamental limit imposed by quantum mechanics. Research led by Cornell University has yielded high-intensity sources of light with quantum levels of noise. Courtesy of Nature Photonics (2025). DOI: 10.1038/s41566-025-01677-2 The discovery stems from a phenomenon that the researchers call "noise-immune quantum correlations." The researchers passed laser pulses to counter the amplification of noise through nonlinear optical fiber and used a programmable spectral filter to isolate the most stable combinations of these frequencies. Some of the filtered combinations showed noise levels 30× lower than the original beam, while the filtered light retained high peak intensities of up to 0.1 TW per square centimeter. To explain the behavior they observed, the researchers developed a model that extracts quantum noise predictions directly from classical simulations of the laser's dynamics. According to Rivera, the model provides a method for subsequent researchers to apply the technique to their own laser systems. Rivera said the idea for the project came from a practical need in his own lab: generating quantum light without purchasing an expensive, low-noise system. The research could eventually extend beyond laboratory experiments, such as for communication systems such as cross-ocean fiber-optic cables that employ the amplification technique to preserve signal quality. “What it means is that now there are so many more laser sources you can use to generate quantum light,” Rivera said. “Amplified sources are super common and they're the easiest, cheapest way to build a high-power laser.” Co-authors include researchers from Boston University, Harvard University, Stanford University, the Technion-Israel Institute of Technology and the University of Central Florida. The research was published in Nature (www.doi.org/10.1038/s41566-025-01677-2).