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Probing quantum and thermal noise in an interacting many-body system

Abstract

The probabilistic character of the measurement process is one of the most puzzling and fascinating aspects of quantum mechanics. In many-body systems quantum-mechanical noise reveals non-local correlations of the underlying many-body states. Here, we provide a complete experimental analysis of the shot-to-shot variations of interference-fringe contrast for pairs of independently created one-dimensional Bose condensates. Analysing different system sizes, we observe the crossover from thermal to quantum noise, reflected in a characteristic change in the distribution functions from poissonian to Gumbel type, in excellent agreement with theoretical predictions on the basis of the Luttinger-liquid formalism. We present the first experimental observation of quasi-long-range order in one-dimensional atomic condensates, which is a hallmark of quantum fluctuations in one-dimensional systems. Furthermore, our experiments constitute the first analysis of the full distribution of quantum noise in an interacting many-body system.

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Figure 1: Experimental set-up and observed interference patterns.
Figure 2: Analysis of the observed interference patterns.
Figure 3: Length dependence of the average contrast.
Figure 4: Distribution functions of the measured interference contrasts for different lengths L.

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Acknowledgements

We acknowledge financial support from the European Union through the contracts MRTN-CT-2003-505032 (Atom chips), Integrated Project FET/QIPC ‘SCALA’, FWF, NSF, Harvard-MIT CUA, AFOSR, Swiss NSF and MURI. We thank S. Groth for fabricating the atom chip used in the experiments and D. A. Smith for critical reading of the manuscript.

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S.H. and J.S. collected the data presented in this article. A.I., V.G., and E.D. provided the theoretical models used. All authors contributed to analysis and interpretation of the data and helped in editing the manuscript.

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Correspondence to J. Schmiedmayer.

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Hofferberth, S., Lesanovsky, I., Schumm, T. et al. Probing quantum and thermal noise in an interacting many-body system. Nature Phys 4, 489–495 (2008). https://doi.org/10.1038/nphys941

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