Parallel plate force metrology: Status and Perspectives

Abstract

The Casimir effect has been investigated intensely both in theory and experiments for more than a quarter of a century. Still, open questions remain that cannot be answered unambiguously with current experiments. One of these questions regards the description of the dielectric response of metals. Precision measurements give clear indications that either zero frequency dissipation has to be neglected at short separations, or alternatively, a non-local response has to be considered. Moreover, current experiments cannot distinguish between the mentioned two approaches, and the situation in the thermal regime remains unclear. Another question regards the discontinuity of the Casimir force at the Mott-Anderson phase transition in semiconductors, where present data, again, do not permit to distinguish between the different models but theory agrees with the experiment only if the response of free charge carriers is neglected for the dielectric state. The Casimir And Non-Newtonian force EXperiment (Cannex) is the first metrological Casimir experiment implementing the geometry of plane-parallel macroscopic plates. This geometry allows us to increase the experimental precision by several orders of magnitude with respect to previous measurements, and thereby discriminate all existing models at distances below and above the thermal wavelength, and for various material combinations. The setup also allows for well-controlled temperature differences between the plates, which brings into reach a quantitative confirmation of the theory of out-of-thermal-equilibrium Casimir forces and radiative heat transfer. After a recent proof of principle, the setup is currently being rebuilt and improved. In this contribution, I will give an update on the construction, and review the numerous options for measurements of Casimir, dark matter, dark energy, and thermal forces.