A new method for photon-number-resolving detectors accurately identifies detection events originating from one, two or three photons with 99 % posterior confidence across all three classes. The dual-trigger technique maps the number of detected photons onto the time difference between when a detector pulse rises and falls; enabling clear separation of these distinct events whilst maintaining precise timing information. This method uses a dual-trigger system to measure both when a detector signal rises and falls, distinguishing between different numbers of incoming photons while preserving precise timing data.

Timings as low as 41ps, a billionth of a second, were demonstrated for detecting two or more photons simultaneously. A specialised camera has been developed for accurately determining the number of photons detected in each burst of light; it doesn’t just detect that light has arrived but attempts to count exactly how many individual ‘packets’ of light, photons, are present.

The technique employs a dual-trigger system on an extremely sensitive digital camera called a superconducting nanowire single-photon detector, measuring both when a signal rises and falls to distinguish between one, two or three incoming photons whilst maintaining precise timing information.

Dual-triggering achieves picosecond timing resolution and multi-photon event classification

Timing jitter fell below 41ps when detecting two or more photons; this is a significant improvement over previous methods that relied on post-processing techniques to resolve variations in timing dependent on photon count. Monitoring both the rising and falling edges of detector pulses allows events to be confidently assigned to one, two, or three photons with 99 % posterior confidence across all three classes across all classes.

Superconducting nanowire single-photon detectors effectively map detected photon numbers onto the time interval between trigger points, enabling clear separation of distinct events while preserving precise arrival times crucial for quantum applications. Further analysis demonstrated constant-fraction discrimination yielded lower jitter for single-photon detections compared with edge triggering alone, whilst maintaining consistent arrival times.

Improved time resolution enables more precise quantum signal analysis

Accurate photon counting is fundamental to many quantum technologies and underpins advances in secure communication and computation. Traditional methods struggle with timing precision when attempting to discern multiple simultaneous arrivals or characterise how detection speed varies depending on particle count. The new dual-trigger approach offers an immediate advantage by resolving this information directly within the detector itself, avoiding computationally intensive post-processing steps common with older systems.

Implementing dual-trigger systems alongside existing single-channel setups may present challenges for established workflows; however, integrating new hardware always requires careful consideration. This technique provides a robust method for discerning the number of photons detected in each light pulse while simultaneously preserving precise timing information important for advanced quantum applications. Consequently, this advancement bypasses conventionally required computational intensity, offering low latency data acquisition ideal for real-time analysis and control within complex photonic systems.

The research demonstrated that a dual-trigger readout scheme successfully assigned detection events to either one, two or three photons with 99% certainty. This is valuable because it allows researchers to resolve the number of photons detected in real time without relying on extensive post-processing calculations.

The team found timing jitter decreased as photon numbers increased, reaching below 41 picoseconds for detections of two or more photons. They also report constant-fraction discrimination offered lower jitter for single-photon events while maintaining consistent arrival times; this work establishes a low-latency method relevant to precision achievable in photonic quantum applications.

👉 More information
🗞 Dual-Trigger of Series Nanowire Detector for Event-Based Photon Number Assignment
✍️ Stefanie Grotowski, Daniel Landes, Fabian Wietschorke, Paul Pucknus, Rasmus Flaschmann, Torsten Langer, Torsten Krause, Kai Müller and Jonathan J. Finley
🧠 ArXiv: https://arxiv.org/abs/2609.08811

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