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Physics

Scalable generation of heralded single photons via active feed-forward switching of a fiber delay line

Xavier Barcons Planas, Helen M. Chrzanowski, Janik Wolters

Featured June 21, 2026

Original Paper

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Simply

By using a clever optical switch and a fiber loop, the system catches and holds single light particles from a random source, releasing them on cue to create a steady stream of synchronized photons for quantum computers.

In depth
The paper introduces a novel free-space-fiber hybrid delay line with feed-forward control to overcome the probabilistic nature of spontaneous parametric down-conversion (SPDC) sources. By actively switching and storing heralded photons in a fiber loop, the system achieves temporal synchronization of multiple photon generation events, significantly enhancing the rate of desired multi-photon states while maintaining high photon quality.

Key Takeaways

  • 1
    The authors developed a hybrid delay line combining fast electro-optic switching (Pockels cells) with low-loss fiber optics for scalable temporal multiplexing.
  • 2
    The system actively synchronizes heralded photons from an SPDC source to an external clock, achieving up to 180-fold rate enhancement for three-photon events.
  • 3
    Utilizing narrow-band, telecom-wavelength photons ensures minimal dispersion and low loss over extended fiber delays, crucial for maintaining photon indistinguishability.

Conceptual Flow

HIGH LEVEL
1
Methodology: Synchronizing Probabilistic Photons

The system takes randomly appearing light particles, uses a fast switch to store them in a loop, and then releases them at exact, scheduled times.

Random Light Particles
Catch and Store
Scheduled Light Particles
2
Results: Boosting Photon Rates

This new method turns a few random light particles into many more scheduled ones, making it much easier to build quantum devices.

Few Random Photons
Multiply and Align
Many Scheduled Photons