In their recent publication, Nathalie Picqué and Theodor Hänsch from the Max Planck Institute of Quantum Optics demonstrate a novel method of broadband high-resolution spectroscopy and interferometry using two femtosecond fiber lasers from Menlo Systems. By attenuating the comb light passing through the sample to the photon level and applying a photon-counting detector, they observe interference of the two frequency combs in the counting statistics. This phenomenon cannot be intuitively explained when assuming that photons exist before detection. The novel method has implications on the detection threshold in measurements with extremely weak signals.

Original publication:
PNAS Vol. 117, p. 26688 (2020)

MPQ Press release:
Not all cats are grey in the dark!

Image courtesy: Nathalie Picqué, MPQ