Science 350, 1343–1346 (2015)

The difficulty in observing random, non-repetitive weak signals that are hidden in noise has caused detection challenges in astronomy, spectroscopy, biology and remote sensing. Now, a team from the University of California at San Diego, USA show that a fast, randomly occurring event can be successfully detected and extracted from a noisy background. Their approach uses instantaneous spectral cloning and a single-step, coherent field processor. More specifically, an 80-ps-long pulse was spectrally cloned and processed to increase the received signal-to-noise ratio by 14.1 dB. To separate signal from noise, the number of spectral copies was varied from 6 to 36, proving that background rejection can be progressively increased even when the random event is immersed in a high level of background noise. The team shows that an isolated 80-ps pulse buried in noise could be detected with a confidence level exceeding 99%. The team says that spectral cloning can be used for more complex analyses of random events, in both the microwave and optical domains.