Atom interferometers are powerful tools for both measurements in fundamental physics and inertial sensing applications. Their performance, however, has been limited by the available interrogation time of atoms freely falling in a gravitational field. By using the mode-filtered laser beam in an optical cavity, we have realized a trapped atom interferometer with 20 seconds of coherence, extending the maximum coherence times of spatially-separated massive quantum superpositions by nearly an order of magnitude . Recent experimental advances have now pushed our lattice interferometer to demonstrate an incredible one-minute of spatial coherence . Our lattice atom interferometer offers unique advantages over traditional free-fall setups, enabling exotic or fundamental potentials such as dark energy , gravity , or blackbody radiation  to be measured by holding, rather than dropping, atoms.
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