Feasible measurement-based entanglement purification in linear optics

Entanglement purification is used to distill high quality entangled states from several noisy low quality entangled states, and it plays a key role in quantum repeater. The measurement-based entanglement purification protocol (MB-EPP) does not require local two-qubit gates or single-particle measurements on the noisy pairs and may offer significant advantages compared with the gate-based EPPs. We present an alternative MB-EPP in linear optics. Subsequently, we provide a detailed analysis on the realization of this MB-EPP using spontaneous parametric down conversion (SPDC) sources. By delicately designing the optical circuits, the double-pair emission noise caused by SPDC sources can be eliminated automatically. Combined with suitable quantum memory and entanglement swapping, this MB-EPP may have application potential in the implementation of a practical measurement-based quantum repeater. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

Entanglement purification is a key technique in quantum repeaters. The measurement-based entanglement purification protocol is advantageous as it does not require local two-qubit gates or single-particle measurements on noisy pairs. By utilizing SPDC sources and carefully designing optical circuits, high-quality entangled states can be distilled effectively.