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arXiv:1702.03159 · Physical Review A

Noise spectroscopy with a quantum gas

Peter Federsel, Carola Rogulj, Tobias Menold, Z. Darázs, P. Domokos, Andreas Günther, József Fortágh

Published Apr 5, 2017• 3 citations
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Abstract

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.

DOI
10.1103/physreva.95.043603

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Microwave fields can be used to drive local spin transitions in quantum gases and for outcoupling of cold atomic beams from magnetic traps. In this paper, we derive an analytic theory for the outcoupling rate as a response to weak microwave fields of varying frequency and power. The theory holds for thermal clouds and Bose-Einstein condensates. It allows for calculating transition rates in arbitrary magnetic trap geometries and includes the effect of gravity. We verify our theory by measuring the flux of outcoupled atoms at the single-particle level. The derived spectral response is important for magnetic noise spectroscopy with quantum gases, and for probing quantum gas dynamics with single atom detectors in real time.
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