Telecom quantum photonic interface for a 40Ca+ single-ion quantum memory

Entanglement-based quantum networks require quantum photonic interfaces between stationary quantum memories and photons, enabling entanglement distribution. Here we present such a photonic interface, designed for connecting a Ca-40(+) single-ion quantum memory to the telecom C-band. The interface combines a memory-resonant, cavity-enhanced spontaneous parametric down-conversion photon pair source with bi-directional polarization-conserving quantum frequency conversion. We demonstrate preservation of high-fidelity entanglement during conversion, fiber transmission over up to 40 km and back-conversion to the memory wavelength. Even for the longest distance and bi-directional conversion the entanglement fidelity remains larger than 95% (98%) without (with) background correction.

Automated summary

Researchers have developed a photonic interface to connect a Ca-40(+) single-ion quantum memory to telecom C-band photons, enabling the distribution of entanglement in quantum networks. The interface utilizes cavity-enhanced spontaneous parametric down-conversion photon pairs and bi-directional polarization-conserving quantum frequency conversion. The team demonstrated the preservation of high-fidelity entanglement during conversion, fiber transmission up to 40 km, and back-conversion to the memory wavelength, with an entanglement fidelity larger than 95% (98%) without (with) background correction, even for the longest distance and bi-directional conversion.