We report on the spectral analysis and the local measurement of intensity correlations of microwave fields using ultracold quantum gases. The fluctuations of the electromagnetic field induce spin flips in a magnetically trapped quantum gas and generate a multimode atom laser. The output of the atom laser is measured with high temporal resolution on the single-atom level, from which the spectrum and intensity correlations of the generating microwave field are reconstructed. We give a theoretical description of the atom-laser output and its correlations in response to resonant microwave fields and verify the model with measurements on an atom chip. The measurement technique is applicable for the local analysis of classical and quantum noise of electromagnetic fields, for example, on chips, in the vicinity of quantum electronic circuits.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics