Scientists from Stockholm University, Nordita, and the University of Tübingen have suggested detecting gravitational waves by observing changes in the light emitted by atoms. The waves would subtly shift photon frequencies in different directions without altering emission rates. This approach could enable compact detectors using cold-atom systems.
Gravitational waves, ripples in spacetime from events like colliding black holes, are typically detected with kilometer-scale instruments measuring tiny distance changes. A theoretical study accepted for publication in Physical Review Letters offers a novel method: examining how these waves affect spontaneous emission from atoms. Atoms release light at specific frequencies when returning to lower energy states, interacting with the quantum electromagnetic field. Gravitational waves modulate this field, shifting emitted photon frequencies directionally, researchers say. Jerzy Paczos, a PhD student at Stockholm University, explained: 'Gravitational waves modulate the quantum field, which in turn affects spontaneous emission. This modulation can shift the frequencies of emitted photons compared with the no-wave case.' The total light emission rate remains unchanged, creating a distinct directional pattern in the spectrum that reveals the wave's direction and polarization, helping distinguish signals from noise. This signature has evaded notice until now because overall brightness stays the same. The idea targets low-frequency waves, relevant for future space missions. Systems like atomic clocks with precise optical transitions and long interaction times in cold-atom setups are promising for tests. Navdeep Arya, a postdoctoral researcher at Stockholm University, noted: 'Our findings may open a route toward compact gravitational-wave sensing, where the relevant atomic ensemble is millimeter-scale.' The authors liken atoms to a steady tone altered directionally by passing waves. While estimates are promising, a thorough noise analysis is needed for feasibility. The study, by Jerzy Paczos, Navdeep Arya, Sofia Qvarfort, Daniel Braun, and Magdalena Zych, was provided by Stockholm University.
