  Quantum repeaters are required for long-distance quantum communication. For
efficient coupling of quantum entangled photon sources with narrow-linewidth
quantum memories we performed the frequency stabilization of two lasers at 1514
and 1010 nm. The 1514 nm pump laser of the entangled photon source exhibited a
frequency stability of 3.6 \times 10^{-12} (\tau = 1 s). The 1010 nm pump laser
of the wavelength conversion system exhibited a frequency stability of 3.4
\times 10^{-12} (\tau = 1 s). The stabilities of both lasers were approximately
two orders of magnitude smaller than the frequency width of 4 MHz of the Pr:YSO
quantum memory. Such frequency-stabilized lasers can realize the remote
coupling of a quantum memory and an entangled photon source in quantum
repeaters.
