A single-crystal source of path-polarization entangled photons at non-degenerate wavelengths.

We demonstrate a bright, narrowband, compact, quasi-phase-matched single-crystal source generating path-polarization-entangled photon pairs at 810 nm and 1550 nm at a maximum rate of 3 x 10(6) s(-1) THz(-1) mW(-1) after coupling to single-mode fiber, and with two-photon interference visibility above 90%. While the source can already be used to implement quantum communication protocols such as quantum key distribution, this work is also instrumental for narrowband applications such as entanglement transfer from photonic to atomic qubits, or entanglement of photons from independent sources.

Narrowband polarization-entangled photon pairs distributed over a WDM link for qubit networks.

We present a bright, narrowband, portable, quasi-phase-matched two-crystal source generating polarization-entangled photon pairs at 809 nm and 1555 nm at a maximum rate of 1.2 x 10(6) s(-1) THz-1 mW(-1) after coupling to single-mode fiber. The quantum channel at 1555 nm and the synchronization signal gating the single photon detector are multiplexed in the same optical fiber of length 27 km by means of wavelength division multiplexers (WDM) having 100 GHz (0.8 nm) spacing between channels. This implementation makes quantum communication applications compatible with current high-speed optical networks.