Feasible measurement-based entanglement purification in linear optics.

Area of Science:

• Quantum Information Science
• Quantum Communication

Background:

• Entanglement purification is vital for distilling high-fidelity entangled states from noisy ones.
• It plays a critical role in the development of quantum repeaters.
• Measurement-based entanglement purification protocols (MB-EPPs) offer potential advantages over gate-based methods by avoiding local two-qubit gates and single-particle measurements.

Purpose of the Study:

• To present an alternative measurement-based entanglement purification protocol (MB-EPP) implemented in linear optics.
• To analyze the practical realization of this MB-EPP using spontaneous parametric down conversion (SPDC) sources.
• To demonstrate noise suppression techniques for practical quantum repeater applications.

Main Methods:

• Development of a novel measurement-based entanglement purification protocol (MB-EPP) using linear optical elements.
• Detailed analysis of the protocol's feasibility with spontaneous parametric down conversion (SPDC) sources.
• Optical circuit design to automatically eliminate double-pair emission noise from SPDC sources.

Main Results:

• An alternative MB-EPP in linear optics is presented.
• The proposed optical circuits effectively eliminate double-pair emission noise inherent in SPDC sources.
• The protocol is compatible with quantum memory and entanglement swapping for enhanced performance.

Conclusions:

• The presented MB-EPP offers a promising approach for high-quality entanglement distillation.
• The protocol's noise mitigation strategies are suitable for practical implementation.
• This MB-EPP has significant potential for building practical measurement-based quantum repeaters.