  High-visibility interference of photon echoes generated in spatially
separated solid-state atomic ensembles is demonstrated. The solid state
ensembles were LiNbO$_3$ waveguides doped with Erbium ions absorbing at 1.53
$\mu$m. Bright coherent states of light in several temporal modes (up to 3) are
stored and retrieved from the optical memories using two-pulse photon echoes.
The stored and retrieved optical pulses, when combined at a beam splitter, show
almost perfect interference, which demonstrates both phase preserving storage
and indistinguishability of photon echoes from separate optical memories. By
measuring interference fringes for different storage times, we also show
explicitly that the visibility is not limited by atomic decoherence. These
results are relevant for novel quantum repeaters architectures with photon echo
based multimode quantum memories.
