Hannover 2010 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 44: Quantum Information: Concepts and Methods III
Q 44.8: Talk
Thursday, March 11, 2010, 12:15–12:30, E 214
Increasing the statistical significance of entanglement detection in experiments — •Bastian Jungnitsch1, Sönke Niekamp1, Matthias Kleinmann1, Otfried Gühne1, He Lu2, Wei-Bo Gao2, Yu-Ao Chen2,3, Zeng-Bing Chen2, and Jian-Wei Pan2,3 — 1Institut für Quantenoptik und Quanteninformation, Innsbruck, Austria — 2Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China — 3Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany
Entanglement is often verified by a violation of an inequality like a Bell inequality or an entanglement witness. Considerable effort has been devoted to the optimization of such inequalities in order to obtain a high violation.
We demonstrate theoretically and experimentally that such an optimization does not necessarily lead to a better entanglement test, if the statistical error is taken into account. Theoretically, we show for different error models that reducing the violation of an inequality can improve the significance. We show this to be the case for an error model in which the variance of an observable is interpreted as its error and for the standard error model in photonic experiments. Specifically, we demonstrate that the Mermin inequality yields a Bell test which is statistically more significant than the Ardehali inequality in the case of a photonic four-qubit state that is close to a GHZ state.
Experimentally, we observe this phenomenon in a four-photon experiment, testing the above inequalities for different levels of noise.