A simple method for the measurement of the refractive indices of parallel plate samples is described that uses the shift of the interference pattern when rotating the sample in one arm of a Mach–Zehnder interferometer. The theoretical fringe pattern shift is calculated and the accuracy of the method is derived. A typical accuracy of about 10−4 can be achieved at low refractive indices. The method is especially useful when—because of other reasons—the samples are provided as plates or when prisms are difficult to fabricate.
We report on single-shot coherent diffractive imaging of isolated helium nanodroplets obtained with intense multicolor XUV pulses from a high harmonic source. The wide-angle scattering patterns yield the droplets' shapes and refractive indices.
The transportable Quantum Gravimeter QG-1 is based on the principle of atom interferometry with collimated Bose-Einstein condensates (BEC) to determine the absolute value of the local gravitational acceleration g, aiming for an unprecedented level of accuracy < 3 nm s−2. The QG-1 uses an atom-chip to produce well-defined magnetic fields, allowing high controllability of the atomic cloud and creating a BEC. After release from the magnetic trap into free fall, using well-controlled laser pulses the BEC is split, each part accumulating phase on its trajectory during free fall, and thereafter recombined, leading to self-interference. From the phase difference of the two parts of the BEC, the local gravitational acceleration g can be determined. Environmental vibrations contribute to the accumulating phase during free fall, leading to a disturbing phase shift of the interfering BEC. By measuring the high-frequency environmental noise with a classical accelerometer, this additional phase shift can be infered and corrected for in the determination of g.In this contribution tide-resolving results of the latest measurement campaign with implemented classical sensors to correct for high-frequency vibrations with an accelerometer and drifts with a tiltmeter will be presented, rendering an important milestone for the development of our QG-1.We acknowledge financial funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project-ID 434617780 - SFB 1464 TerraQ and under Germany’s Excellence Strategy - EXC 2123 QuantumFrontiers, Project-ID 390837967.
