Stability of a trapped-atom clock on a chip

Abstract

We present a compact atomic clock interrogating ultracold 87Rb magnetically\ntrapped on an atom chip. Very long coherence times sustained by spin\nself-rephasing allow us to interrogate the atomic transition with 85% contrast\nat 5 s Ramsey time. The clock exhibits a fractional frequency stability of\n$5.8\\times 10^{-13}$ at 1 s and is likely to integrate into the\n$1\\times10^{-15}$ range in less than a day. A detailed analysis of 7 noise\nsources explains the measured frequency stability. Fluctuations in the atom\ntemperature (0.4 nK shot-to-shot) and in the offset magnetic field\n($5\\times10^{-6}$ relative fluctuations shot-to-shot) are the main noise\nsources together with the local oscillator, which is degraded by the 30% duty\ncycle. The analysis suggests technical improvements to be implemented in a\nfuture second generation set-up. The results demonstrate the remarkable degree\nof technical control that can be reached in an atom chip experiment.\n