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SYAD: Symposium SAMOP Dissertation-Prize 2018

SYAD 1: SAMOP Dissertation-Prize

SYAD 1.2: Invited Talk

Tuesday, March 6, 2018, 11:00–11:30, B Audimax

Testing the Quantumness of Atom Trajectories — •Carsten Robens — Institut für Angewandte Physik der Universität Bonn, Wegelerstr. 8, 53115 Bonn — Massachusetts Institute of Technology, Center for Ultracold Atoms, Research Laboratory of Electronics, and Department of Physics, 77 Mass Ave, Cambridge, MA 02139

I will present experiments using individual atoms in optical lattices to test the quantumness of atom trajectories both in a single- and two-particle atom interferometer. These results rely on so-called polarization-synthesized optical lattices—a novel implementation of state-dependent transport—which achieves an unprecedented control over the position of individual atoms with angstrom precision.

At the single-particle level, I conducted a rigorous test of the superposition principle using the Leggett-Garg inequality. Despite the indisputable success of quantum mechanics in describing the microscopic world, it is still an unresolved question how to explain the wave function reduction, which has led to the development of several theories. In 1985 Leggett and Garg derived an inequality that provides an objective criterion to discern quantum- from macro-realistic theories. Our experiment demonstrates for the first time that the trajectories of a single atom are truly nonclassical and our findings constrain macro-realistic theories. Our delocalized Cesium atoms are the most macroscopic objects that have been used to experimentally test the Leggett-Garg inequality using noninvasive measurements.

At the two-particle level, I demonstrate Hong-Ou-Mandel interference between two indistinguishable Cesium atoms. This experiment embodies the fundamental building block of a boson sampling machine, a specialized type of quantum computer, which holds promise to demonstrate a speedup of quantum over classical devices in the near future.