Rotating Michelson-Morley experiment based on a dual cavity cryogenic sapphire oscillator

Abstract

Recent experiments based on cryogenic microwave oscillators [1,2,3] have tested the isotropy of the speed of light (Michelson-Morley experiment) at sensitivities of the order of a part in 1015, which is a similar sensitivity to other best tests [4,5]. Further improvements of the accuracy in this type of experiment are not expected due to the already long data set and the systematic error limit [3]. We have constructed a new rotating Michelson-Morley experiment consisting of two cylindrical cryogenic sapphire resonators. The temperature of the dual cavity is controlled at approximately 6 K where the beat frequency between two oscillators is independent on temperature. By rotating the experiment an improvement of several orders of magnitude in our sensitivity to light speed anisotropy is expected, as the relevant time variations will now be at the rotation frequency where the frequency stability of the cryogenic oscillators is the best.