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arXiv · 1503.08433

Quantum non-demolition measurement enables macroscopic Leggett-Garg tests

Costantino Budroni·Giuseppe Vitagliano·Giorgio Colangelo·Robert J. Sewell·Otfried Gühne·Geza Toth·Morgan Mitchell
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Abstract

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.

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Costantino Budroni, Giuseppe Vitagliano, Giorgio Colangelo, Robert J. Sewell, Otfried Gühne, Geza Toth, Morgan Mitchell. 2015-03-29. Quantum non-demolition measurement enables macroscopic Leggett-Garg tests. https://doi.org/10.1103/physrevlett.115.200403

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