  Compared to light interferometers, the flux in cold-atom interferometers is
low and the associated shot noise large. Sensitivities beyond these limitations
require the preparation of entangled atoms in different momentum modes. Here,
we demonstrate a source of entangled atoms that is compatible with
state-of-the-art interferometers. Entanglement is transferred from the spin
degree of freedom of a Bose-Einstein condensate to well-separated momentum
modes, witnessed by a squeezing parameter of -3.1(8) dB. Entanglement-enhanced
atom interferometers open up unprecedented sensitivities for quantum
gradiometers or gravitational wave detectors.
