Quantum test of the Universality of Free Fall using rubidium and potassium

We report on an improved test of the Universality of Free Fall using a rubidium-potassium dual-species matter wave interferometer. We describe our apparatus and detail challenges and solutions relevant when operating a potassium interferometer, as well as systematic effects affecting our measurement. Our determination of the Eotvos ratio yields η Rb,K  = −1.9 × 10−7 with a combined standard uncertainty of σ η = 3.2 × 10−7 .