Detection of light quanta in superconducting nano- and microwires is the key enabling technology for fields ranging from quantum optics and quantum photonics to emerging applications like dark matter searches. However, recent progress in accessing lower photon energies or utilizing high-temperature superconductors reveals substantial gaps in understanding quantum detection physics and calibrating photonic quantum systems. To bridge these gaps, we develop a universal model that incorporates spatially and energy-resolved detection physics, essential for photonic quantum sensors. We validate our approach using modern MgB2 nanowire detectors, retrieving their detection threshold and its intrinsic energy blur, by disentangling the complex statistics of single- and multi-photon detection. Our model can augment quantum detector tomography by embedding physical constraints, and it offers a practical tool for modeling and engineering a broad class of detectors under diverse operating conditions.
Detection of light quanta in superconducting nano- and microwires is the key enabling technology for fields ranging from quantum optics and quantum photonics to emerging applications like dark matter searches. However, recent progress in accessing lower photon energies or utilizing high-temperature superconductors reveals substantial gaps in understanding quantum detection physics and calibrating photonic quantum systems. To bridge these gaps, we develop a universal model that incorporates spatially and energy-resolved detection physics, essential for photonic quantum sensors. We validate our approach using modern MgB2 nanowire detectors, retrieving their detection threshold and its intrinsic energy blur, by disentangling the complex statistics of single- and multi-photon detection. Our model can augment quantum detector tomography by embedding physical constraints, and it offers a practical tool for modeling and engineering a broad class of detectors under diverse operating conditions.
Detection of light quanta in superconducting nano- and microwires is the key enabling technology for fields ranging from quantum optics and quantum photonics to emerging applications like dark matter searches. However, recent progress in accessing lower photon energies or utilizing high-temperature superconductors reveals substantial gaps in understanding quantum detection physics and calibrating photonic quantum systems. To bridge these gaps, we develop a universal model that incorporates spatially and energy-resolved detection physics, essential for photonic quantum sensors. We validate our approach using modern MgB2 nanowire detectors, retrieving their detection threshold and its intrinsic energy blur, by disentangling the complex statistics of single- and multi-photon detection. Our model can augment quantum detector tomography by embedding physical constraints, and it offers a practical tool for modeling and engineering a broad class of detectors under diverse operating conditions.
Abstract Detection of light quanta in superconducting nano- and microwires is the key enabling technology for fields ranging from quantum optics and quantum photonics to emerging applications like dark matter searches. However, recent progress in accessing lower photon energies or utilizing high-temperature superconductors reveals substantial gaps in understanding quantum detection physics and calibrating photonic quantum systems. To bridge these gaps, we develop a universal model that incorporates spatially and energy-resolved detection physics, essential for photonic quantum sensors. We validate our approach using modern MgB2 nanowire detectors, retrieving their detection threshold and its intrinsic energy blur, by disentangling the complex statistics of single- and multi-photon detection. Our model can augment quantum detector tomography by embedding physical constraints, and it offers a practical tool for modeling and engineering a broad class of detectors under diverse operating conditions.
The ability to detect single photons in the mid-infrared spectral range (beyond 2 μm wavelength, photon energy below 0.62 eV) is the key to unlocking a range of emerging scientific applications, from remote sensing LIDAR, molecular spectroscopy, and powerful new approaches to dark matter detection. Conventional detector types, such as semiconductor single-photon avalanche diodes, lose sensitivity at such low photon energy. Superconducting materials, with a much lower characteristic energy gap, hold particular promise. In this Perspective, we focus on recent advances in superconducting nanowire single-photon detectors, which have recently extended single-photon sensitivity up to 29 μm (0.043 eV). We discuss the potential for future advances and strategies to overcome challenges to technological development.
In this talk, I will present the latest results in superconducting single-photon detectors. Superconducting wires have remarkable sensitivity to single-photons and are a reliable and high-performance technology with significant impact on the quantum information research community. However, increasingly applications as diverse as detection of high-energy particles and searches for dark matter are being pursued. Finally, research on these nanowires has permitted their use for basic electronics circuits such as comparators, shift registers, and counters. We will review these and other topics surrounding the development of nanowire single-photon detectors.
Superconducting nanowires have been used to detect single photons for more than 20 years. The basic principle is that photons can perturb superconducting Cooper pairs and thereby create a resistive hotspot, which produces a current-crowding effect. This current-crowding effect reduces the superconducting energy gap near the hotspot, which results in the nanowire changing from a superconducting to a normal state near the hotspot. The resulting high impedance causes the current to be squeezed into a high frequency coaxial wire connected in parallel with it, which finally produces a measurable voltage pulse. Thanks to the maturity of current micro- and nano- fabrication techniques, high quality superconducting thin films and nano-wires have been realized in a variety of materials such as NbN, WSi, MoSi and others. These techniques include magnetron sputtering, physical vapor deposition, electron beam lithography, optical lithography, reactive ion etching, wafer cutting, etc. Measurements of superconducting single-photon detectors require cryogenic refrigeration systems, ranging from the initial liquid helium cold tank, to modern dry dilution refrigerators. On one hand, a superconducting device needs to be cooled down below its critical temperature to work. On the other hand, photon-detection events generate hot spots, which release heat to the device substrate, which the refrigerator needs to efficiently take away. Research on superconducting nanowire single-photon detectors (SNSPDs) has made significant advancements over the past two decades, including high detection efficiency, low dark counts, and broad wavelength range capabilities. Beyond improvements in traditional NbN, WSi and MoSi superconducting nanowires, there have been numerous efforts to develop high-temperature superconducting nanowires, such as MgB2 and Bi2Sr2CaCu2O8 (BSCCO), due to the operational limitations imposed by low-temperature superconducting materials. Typically, single-photon detectors require operation temperatures below the critical temperature. High-temperature superconducting nanowire single-photon detectors have currently reported to exhibit the highest operating temperature around 20 K in BSCCO, which is much lower than its critical temperature of 80 K, showing that large-gap superconductors have a comparably low sensitivity to low-energy photons. In recent years since 2018, several groups have reported that micrometer-wide superconducting wires can also be used for single-photon detection, unlike the conventional nanometer-wide superconducting wires. In general, as long as the bias current is uniformly distributed in superconducting wires and approaches the critical Cooper pair-breaking current, the hot spots generated by photon absorption can induce vortices and anti-vortices, and their motion under the action of the Lorentz force generates resistance and voltage, which ultimately produces a normal state region. An increase of the wire width to the micron scale offers more freedom to design new detectors based on current nano- and microfabrication techniques. In this doctoral dissertation, I will first introduce the basic Ginzburg-Landau theory of superconductivity and the measurement theory of superconducting circuits related to single-photon detection. I will then provide a detailed description of the equipment construction and sample fabrication techniques used in the experiment. Finally, I will present my two main studies: in one project I examined the photon-detection performance of superconducting micro-wires with a multi-pinhole structure, the correlation between dark counts and magnetic vortices, as well as the properties of critical current in magnetic fields. In a subsequent study I conducted numerical simulations using the time dependent Ginzburg-Landau equation, to analyze the dynamics of vortices in superconducting micro-strips with regular large-area perforations by pinholes as a function of magnetic field and bias current. The thus obtained predictions were then successfully confirmed in a detailed experimental study on a series of microwires.
Single-photon detection possibility is a fundamental requirement for quantum technologies, including communication, computing and sensing. To achieve scalability and practical deployment, increasing attention is being directed toward integration of detectors with photonic integrated circuits, which offer compactness and compatibility with mass production. Superconducting nanowire single-photon detectors have emerged as the leading solution, combining near-unity efficiency, high temporal performance and the ability to be embedded across a wide range of photonic material platforms. In this review we trace the development of integrated superconducting nanowire single-photon detectors from early demonstrations to recent advances, outlining the progress in device architectures, material engineering and integration strategies. We also discuss performance benchmarks, emerging alternative designs, the future opportunities and challenges for this rapidly evolving field.