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On the observation of nonclassical excitations in Bose–Einstein condensates

Finke, Andreas; Jain, Piyush; Weinfurtner, Silke


Andreas Finke

Piyush Jain


In the recent experimental and theoretical literature well-established nonclassicality criteria from the field of quantum optics have been directly applied to the case of excitations in matter-waves. Among these are violations of Cauchy–Schwarz inequalities, Glauber–Sudarshan P-nonclassicality, subPoissonian number-difference squeezing (also known as the two-mode variance) and the criterion of nonseparability. We review the strong connection of these criteria and their meaning in quantum optics, and point out differences in the interpretation between light and matter waves. We then calculate observables for a homogeneous Bose–Einstein condensate undergoing an arbitrary modulation in the interaction parameter at finite initial temperature, within both the quantum theory as well as a classical reference. We conclude that to date in experiments relevant for this scenario nonclassical effects have not conclusively been observed and conjecture that additional, noncommuting, observables have to be measured to this end. Moreover this has important implications for proposed analog gravity models where the observation of nonclassical effects is a major goal.


Finke, A., Jain, P., & Weinfurtner, S. (2016). On the observation of nonclassical excitations in Bose–Einstein condensates. New Journal of Physics, 18(113017),

Journal Article Type Article
Acceptance Date Sep 21, 2016
Publication Date Nov 8, 2016
Deposit Date Feb 27, 2017
Publicly Available Date Feb 27, 2017
Journal New Journal of Physics
Electronic ISSN 1367-2630
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 18
Issue 113017
Keywords nonclassicality, analogue gravity, Bose–Einstein condensates, Bogoliubov theory, Gross-Pitaevskii equation, parametric resonance, quantum correlations
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