  Inertial sensors based on cold atoms have great potential for navigation,
geodesy, or fundamental physics. Similar to the Sagnac effect, their
sensitivity increases with the space-time area enclosed by the interferometer.
Here, we introduce twin-lattice atom interferometry exploiting Bose-Einstein
condensates. Our method provides symmetric momentum transfer and large areas in
palm-sized sensor heads with a performance similar to present meter-scale
Sagnac devices.
