  The hybrid quantum network, a universal form of quantum network which is
aimed for quantum communication and distributed quantum computation, is that
the quantum nodes in it are realized with different physical systems. This
universal form of quantum network can combine the advantages and avoid the
inherent defects of the different physical system. However, one obstacle
standing in the way is the compatible photonic quantum interface. One possible
solution is using non-degenerate, narrow-band, entangled photon pairs as the
photonic interface. Here, for the first time, we generate nondegenrate
narrow-band polarization-entangled photon pairs in cavity-enhanced spontaneous
parametric down-conversion process. The bandwidths and central wavelengths of
the signal and idler photons are 9 MHz at 935 nm and 9.5 MHz at 880 nm, which
are compatible with trapped ion system and solid-state quantum memory system.
The entanglement of the photon source is certified by quantum state tomography,
showing a fidelity of 89.6% between the generated quantum state with a Bell
state. Besides, a strong violation against Bell inequality with 2.36+/-0.03
further confirms the entanglement property of the photon pairs. Our method is
suitable for the hybrid quantum network and will take a big step in this field.

Quantum Physics