Ultracold Potassium for Atom chip based Interferometry

We report on progress to cool K to BEC on an atom chip for atom interferometry experiments. We are developing a spin-dependent atom interferometer based on AC Zeeman traps, which will have enhanced sensitivity and spatial resolution. K are well suited for AC Zeeman force. In particular, $^{\mathrm{41}}$K has a small hyperfine splitting of 254 MHz, which is low enough to enable easy coupling to an atom chip. Also, $^{\mathrm{41}}$K benefits from suppressed sensitivity to magnetic field noise at 24 G and 45 G. Our apparatus uses an atom chip to trap ultracold atoms 100$\mu $m from the chip.This close proximity to the chip ensures that the atoms experience a strong RF and microwave field gradients that are necessary for using AC Zeeman. We have successfully trapped over 3x10$^{\mathrm{6}}$ atoms at 100$\mu $K with a P of 10$^{\mathrm{-6}}$. At present, we are working to cool $^{\mathrm{41}}$K directly or with Rb. Once the $^{\mathrm{41}}$K atoms have been cooled to sub-$\mu $K levels, or to BEC, then they can be used for interferometry experiments. An interferometer based on $^{\mathrm{41}}$K BEC is a stepping stone towards the creation of a multi-mode interferometer that can work with ultracold thermal atoms or a degenerated Fermi gas.