Transforming passive key relay constellations into an active global quantum internet mesh via spaceborne entangled photon sources and Bell state analyzers.
Periodically poled lithium niobate (PPLN) crystals pumped by continuous-wave diode lasers produce polarization-entangled photon pairs at rates exceeding 20 million pairs/second with Bell state fidelity > 99.1%, shielded against cosmic radiation and temperature extremes.
When two satellites distribute photons to a central orbital node, a two-photon Hong-Ou-Mandel interference measurement projects the distant endpoints into an entangled Bell state, establishing direct quantum correlation across 10,000 km without trusted node assumptions.