PicoQuant has released UniHarp 1.2 and a new version of snAPI, introducing several new capabilities for advanced photon-counting experiments. The centerpiece is Photon Number Resolution (PNR): a method that goes significantly beyond conventional on/off detection and is now directly integrated into both software packages.
What is New in UniHarp 1.2 and snAPI
New measurement class: Histogram 2D The new Histogram 2D class enables the simultaneous evaluation of multiple timing and signal parameters, making it a powerful tool for real-time photon-number discrimination with SNSPDs. It includes Recovery Time Correction, which compensates for pulse distortion at high count rates and extends the practical range of reliable PNR analysis.
New measurement class and manipulator: Export & Import Export and Import facilitate synchronized multi-device workflows by sharing time-tagged data between instruments. This enables channel combination, cross-device coincidence processing, and centralized analysis with configurable channel selection and timing alignment.
New manipulator: Coincidences The extended Coincidences manipulator enables parallel evaluation of multiple channel groups in one step, generating one manipulated channel per group. This provides efficient, scalable processing for multi-photon and correlation analyses.
Extended documentation: UniHarp manual The updated UniHarp manual provides detailed guidance on the new measurement classes and workflows, with in-depth explanations, use cases, and step-by-step instructions for advanced analyses.
Expanded examples: Quantum optics demo codes for snAPI The new snAPI release includes ready-to-use implementations of advanced multi-photon experiments, including Bell-state measurements, GHZ-state heralding, BB84 quantum key distribution, boson sampling with multi-fold coincidences, and coincidence-conditional g².
What is Photon Number Resolution?
Most photon-counting detectors operate in a binary mode: they register whether a photon was detected or not. Photon Number Resolution takes this a step further. Instead of simply registering a detection event, PNR decodes exactly how many photons arrived in a single event, giving researchers direct access to photon statistics and multi-photon processes.
This capability is particularly relevant for experiments based on superconducting nanowire single-photon detectors (SNSPDs), where subtle differences in detector response — such as slew rate, pulse width, amplitude, or timing relative to sync — carry photon-number information that can be extracted and analyzed. PNR is a key method in quantum optics and photonics, with applications ranging from photonic quantum computing and quantum communication to advanced sensing and the characterization of light sources and detectors.
Compatible Instruments
UniHarp 1.2 and snAPI are fully compatible with PicoQuant’s time-tagging electronics, including the HydraHarp 500 and PicoHarp 330.
Free Downloads
Both software packages are available free of charge.
Download UniHarp 1.2 from our Downloads page.
Download snAPI from GitHub.
Learn more about Photon Number Resolution on our dedicated method page.