Quantum Tests of the Universality of Free Fall

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• Dennis Schilpper (Hanover)
• Friday 11 December 2015, 11:00-12:00
• Physics East 217.

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In the process of formulating a “theory of everything” aiming to provide a self-contained model of modern physics by unifying all four fundamental interactions, two theoretical frameworks have yielded invaluable contributions: quantum field theory, which explains the nature of physics at the most microscopic length scales, and Einstein’s general relativity, that conveys our understanding of gravity over the largest distances across the universe. Although no theory of “quantum gravity” consistent over all energy scales exists to date, certain modifications enable a reconciliation of quantum mechanics and general relativity. These approaches allow for violations of the universality of free fall (UFF), which among Lorentz invariance and local position invariance constitute Einstein’s equivalence principle. The UFF states that all bodies, located at the same space-time point, experience the same acceleration in a gravitational field independently of their composition. Because of its central role in modern physics the UFF has been tested extensively, mostly with macroscopic test masses [1]. Matter wave interferometers resemble a novel test method that differs fundamentally from experiments employing macroscopic test masses. We report on a quantum test of the UFF at a 100 ppb uncertainty using two different chemical elements, 39K and 87Rb [2]. We show recent improvements of the experiment and recent progress towards a ppb test aided by the use of a common optical dipole trap as a source. We furthermore present future strategies for tests of the UFF aiming for accuracies of parts in 10^13 and beyond. These approaches comprise experiments realizing free fall times on the order of seconds in Very Long Baseline Atom Interferometry [3] (VLBAI) and the use of novel experimental concepts and the alkaline earth-like element ytterbium.

References

[1] S. Schlamminger et al., Phys. Rev. Lett. 100, 041101– (2008)

[2] D. Schlippert et al., Phys. Rev. Lett. 112, 203002 (2014)

[3] J. Hartwig et al., New J. Phys. 17, 035011– (2015)

This talk is part of the Cold Atoms series.

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