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Updated: Aug 15, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Entanglement distribution: to herald or not to herald
Zero-added-loss multiplexing (ZALM) offers higher entanglement distribution rates than unheralded sources when using many spectral islands and single quantum memories. However, unheralded sources perform better with more quantum memories per island.
Area of Science:
- Quantum communication
- Quantum optics
- Photonics
Background:
- High-rate, high-fidelity entanglement distribution is crucial for quantum internet development.
- Spontaneous parametric downconversion (SPDC) sources are key for generating entangled photon pairs.
- Phase-matched spectral islands in SPDCs enable wavelength-division multiplexing and single-mode temporal behavior.
Purpose of the Study:
- Compare entanglement distribution rates between islands-based zero-added-loss multiplexing (ZALM) and unheralded Sagnac SPDC sources.
- Analyze the impact of heralding efficiency and quantum memory allocation on distribution rates.
- Evaluate the trade-offs in equipment requirements for both systems.
Main Methods:
- Experimental comparison of ZALM (using idler heralding) and unheralded Sagnac SPDC.
- Varied number of spectral islands (N_I) and quantum memories per pump pulse (N_M).
- Measured per-pump-pulse entanglement distribution rates under different configurations.
Main Results:
- ZALM significantly exceeds unheralded rates with >=10 islands and N_M=1.
- Unheralded sources outperform ZALM when N_M = N_I.
- ZALM requires two matched Sagnac sources and high heralding efficiency for optimal performance.
Conclusions:
- The choice between ZALM and unheralded SPDC depends on spectral island and quantum memory configurations.
- ZALM is advantageous for specific quantum internet architectures requiring high heralding efficiency.
- Equipment complexity and heralding efficiency are critical factors in system selection.
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