Hannover 2016 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 3: Quantum Information: Concepts and Methods I

Q 3.3: Vortrag

Montag, 29. Februar 2016, 11:30–11:45, e214

Quantum non-demolition measurement enables macroscopic Leggett-Garg tests — •Costantino Budroni1, Giuseppe Vitagliano2, Giorgio Colangelo3, Robert J. Sewell3, Otfried Gühne1, Geza Tóth2, and Morgan W. Mitchell31Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Walter-Flex-Str. 3, D-57068 Siegen, Germany — 2Department of Theoretical Physics, University of the Basque Country UPV/EHU, P.O. Box 644, E-48080 Bilbao, Spain — 3ICFO – Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain

We show how a test of macroscopic realism based on Leggett-Garg inequalities (LGIs) can be performed in a macroscopic system. Using a continuous-variable approach, we consider quantum non-demolition (QND) measurements applied to atomic ensembles undergoing magnetically-driven coherent oscillation. We identify measurement schemes requiring only Gaussian states as inputs and giving a significant LGI violation with realistic experimental parameters and imperfections. The predicted violation is shown to be due to true quantum effects rather than to a classical invasivity of the measurement. Using QND measurements to tighten the “clumsiness loophole” forces the stubborn macrorealist to re-create quantum back action in his or her account of measurement.


C. Budroni, G. Vitagliano, G. Colangelo, R.J. Sewell, O. Gühne, G. Tóth, and M.W. Mitchell Phys. Rev. Lett. 115, 200403 (2015)

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