〈Q|School Single Photonics Short Course

| 日期 29 August 2025

〈Q|School Single Photonics Short Course: Sources, Detectors and Measurements​

The Swabian Instruments USA team recently had the opportunity to support and attend the 〈Q|School Single Photonics Short Course: Sources, Detectors and Measurements​, presented by CU|Bit> (CU Boulder) and NIST. The〈Q| School brought together leading researchers, startup professionals, and industry partners to share progress and challenges in building the quantum technologies of tomorrow. For Swabian Instruments, it was an excellent opportunity to exchange ideas and better understand the needs driving next-generation experiments.

This course is designed to educate both students and professionals on the full spectrum of single photonics, covering topics such as detectors and sources, measurement techniques, uncertainties, use cases, and engineering considerations like cryogenics and optics. This course is for everyone: technologists, engineers, and students who are looking either for an introduction into single photonics or to deepen their understanding, researchers looking to better understand and express their experiments, and the experienced supporters, too, looking to further educate themselves. Our team found the lectures and labs to be a great way to further expand our knowledge and perspective within the field of single photonics.

Short Course Highlights: Single Photonics Lectures, Labs and Demonstrations

Lab Stations

• Keysight and NIST: Fiber Splicing, Connectors, Verification, and Alignment
  In this lab, students connected optical fibers through fusion splicing to understand the method as a lower-loss alternative to mechanical connectors. Students stripped and cleaned the fiber, then cleaved it by stretching, clamping, and running a blade through it. The fiber verification and alignment station evaluated the intrinsic noise of a detector with a frequency counter.
• Thorlabs: The Quantum Education Kit for Correlation Measurements
  The Thorlabs Quantum Optics Educational Kit was introduced for training on alignment and adjustment of optical components. The kit features Swabian Instruments’ Time Tagger 20 EDU version as the time-to-digital converter to perform coincidence counting from a heralded single-photon source.
• Hamamatsu: Hands-on PMT demonstration
  Hamamatsu showcased their photomultiplier tubes (PMTs) for single photon counting applications.
• Quantum Opus Supeconducting Nanowire Single Photon Detectors (SNSPDs)
  In the Quantum Opus lab, participants were introduced to the differences in SNSPD performance at varying wavelengths: 780 nm, 1064 nm, and 1550 nm. This lab used a laser, a 1550nm optical fiber, a Quantum Opus SNSPD detector, and a Time Tagger Ultra Performance to demonstrate a live time-of-flight (ToF) experiment.
• NIST: Quantum Measurement
  This lab demonstrated a method of inferring an input voltage, a classical quantity, from a measurement of light correlations in a Hanbury Brown and Twiss interferometer, typically used in quantum optics to characterize single photon sources. A coherent source is shone onto a rotating glass to produce a speckled signal that is detected by a pair of Single Photon Avalanche Diode (SPAD) detectors and captured by the Time Tagger Ultra to evaluate signal correlation via a bidirectional histogram. This lab promotes “thinking outside the box” – it educates students on using unconventional modalities enabled by photon counting to achieve a measurement advantage.

Lectures in Single-Photonics Devices, Measurements, and Engineering

With each day having a different theme, we learned from experienced key players in the field.

• Day One: Introduction to the Engineering
  The engineering that drives single photonics was the focus of day one. To begin, we looked at a broad overview of single photon counting: what parameters are important, and how do we define and measure these parameters. Exploring quantum photonics in industry, we then learned about quantum dots and how they can be used to scale quantum computers through interconnects, solving the challenge of limited monolithic architecture. Further, we delved into the limitations of AI hardware and how superconducting optoelectronic networks (SOENs) can contribute to gains in efficiency and speed while reducing cost. Moving into lectures about quantum networks, the lectures explained the difference between classical and quantum networks and how quantum networking manifests itself in real-world applications. Because these experiments suffer from increased noise due to thermal effects, it was important that we discuss cryostats: the differences between various types of cryostats, ideal cooling methods for different applications, and examples of on-chip and on-wafer cryogenic testing. Lastly, the lectures then covered the quantification of uncertainty in single-photon experiments.
• Day Two: Detectors
  Day two lectures were primarily focused on detectors, with emphasis on characterization and optimally run experiments. The course began with an introduction to single-photon detectors (SPDs) and how they work. We then explored the engineering, fundamentals, and performance of various types of detectors and how they may be arranged into arrays: Photomultiplier Tubes (PMTs), Single-photon Avalanche Diode Detectors (SPADs), Superconducting Nanowire Single-Photon Detectors (SNSPDs), and Optical Transition-Edge Sensors (TES). From there, we learned about detector characterization through autocorrelation and the differences between SPDs. Finally, the lecture reviewed choosing a detector for your application by carefully reading detector specifications.
• Day Three: Sources
  After reviewing detectors on day two, day three moved on to what a single-photon source is, how they are characterized, and how they manifest in real-world experiments. The lectures began with indistinguishability and entanglement, and how it is stronger than classical correlation, during which we learned about time-resolved Hong Ou Mandel Interferometry. We then explored different sources and their design, including atoms, ions, quantum dots, and Spontaneous Parametric Down-Conversion (SPDC) sources.
• Day Four: Measurements and Calibration
  The final day of lectures focused on single-photon detector efficiency characterization and measurements. This included learning the importance of SI traceability, the methods by which photon detectors are calibrated, and tomography. We also learned about the metrics by which detectors are characterized: timing jitter, counting, photon number distributions, and resolution (PNR) with SNSPDs. This day tied everything together, taking the things that we individually learned each day and situating them within the context of applicability and compatibility in real-world experiments.

The〈Q|School Single Photonics Short Course on sources, detectors, and measurements gave participants hands-on experience in single-photonics, and provided a space for students to connect theories learned in lecture to the concepts practiced at each lab station. At Swabian Instruments, we remain committed to working alongside researchers, startups, and telecom partners to help bridge the gap between laboratory breakthroughs and scalable quantum systems.

We are extremely grateful to the NIST/CU Boulder coordinators, the other partners, and the participants for the opportunity to deepen our knowledge and learn alongside such a dedicated community of researchers.

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