The increasing level of control over individual quantum systems provides access to hitherto unachieved parameter and resolution regimes for novel tests of quantum theory [1]. Our goal is to exploit this regime.

Jointly with Anton Zeilinger's group we have performed tests of a new incompatibility theorem for a broad class of nonlocal realistic hidden-variable theories [2, 3] that had been suggested by Leggett [4]. Our current focus is on massive mechanical resonators, which are now becoming gradually available for the study of macroscopic quantum phenomena [5].

[1] M. Aspelmeyer, A. Zeilinger, A quantum renaissance, Physics World 21, No.7, July 2008

[2] S. Gröblacher, T. Paterek, R. Kaltenbaek, C. Brukner, M. Zukowski, M. Aspelmeyer, A. Zeilinger, An experimental test of non-local realism, Nature 446, 871-875 (2007)

[3] T. Paterek, A. Fedrizzi, S. Gröblacher, T. Jennewein, M. Zukowski, M. Aspelmeyer, A. Zeilinger, Experimental test of non-local realistic theories without the rotational symmetry assumption, Phys. Rev. Lett. 99, 210406 (2007)

[4] A. J. Leggett, Nonlocal Hidden-Variable Theories and Quantum Mechanics: An Incompatibility Theorem, Found. Phys. 33, 1469 (2003).

[5] M. Arndt, M. Aspelmeyer, A. Zeilinger, How to extend quantum experiments, Fortschr. Phys. 57, 1153 (2009).