Reaching the intrinsic performance limits of superconducting nanowire single-photon detectors up to 0.1 mm wide
Kristen M. Parzuchowski, Eli A. Mueller, Bakhrom Oripov, Benedikt Hampel, Ravin A. Chowdhury, Sahil R. Patel, Daniel Kuznesof, Emma Batson, Ryan Morgenstern, Robert H. Hadfield, Varun Verma, Matthew D. Shaw, Jason P. Allmaras, Martin J. Stevens, A. Gurevich, Adam N. McCaughan
Superconducting nanowire single-photon detectors combine high detection efficiency, low noise, and excellent timing resolution, making them a leading platform for photon-counting applications. However, despite decades of materials and fabrication research, detector performance has never been shown to match theoretical performance expectations. Here, we demonstrate in situ tuning of a detector from its typical, suboptimal operation, to a regime limited only by material quality, allowing the device to reach its intrinsic performance limit. Our approach is based on current-biased superconducting “rails” placed on either side of the detector that redistribute current across its width to achieve peak performance. This technique reduces the dark count rate by 10 orders of magnitude. Further, we show operation at this intrinsic performance limit for devices up to 0.1 mm wide and also demonstrate near-unity internal detection efficiency at a wavelength of 4 µm for a 20 µm wide detector—a factor of 20 wider than the current state of the art. This work enables future detectors to overcome the Pearl limit for device width, paving the way for arbitrarily large detectors.
Superconducting nanowire single-photon detectors combine high detection efficiency, low noise, and excellent timing resolution, making them a leading platform for photon-counting applications. However, despite decades of materials and fabrication research, detector performance has never been shown to match theoretical performance expectations. Here, we demonstrate in situ tuning of a detector from its typical, suboptimal operation, to a regime limited only by material quality, allowing the device to reach its intrinsic performance limit. Our approach is based on current-biased superconducting “rails” placed on either side of the detector that redistribute current across its width to achieve peak performance. This technique reduces the dark count rate by 10 orders of magnitude. Further, we show operation at this intrinsic performance limit for devices up to 0.1 mm wide and also demonstrate near-unity internal detection efficiency at a wavelength of 4 µm for a 20 µm wide detector—a factor of 20 wider than the current state of the art. This work enables future detectors to overcome the Pearl limit for device width, paving the way for arbitrarily large detectors.
Superconducting nanowire single-photon detectors (SNSPDs) combine high detection efficiency, low noise, and excellent timing resolution, making them a leading platform for photon-counting applications. However, despite decades of materials and fabrication research, detector performance has never been shown to match theoretical performance expectations. Here, we demonstrate for the first time in situ tuning of a detector from its typical, suboptimal operation, to a regime limited only by material quality, allowing the device to reach its intrinsic performance limit. Our approach is based on current-biased superconducting "rails" placed on either side of the detector that redistribute current across its width to achieve its peak performance. This technique reduces the dark count rate by ten orders of magnitude. Further, we show operation at this intrinsic performance limit for devices up to 0.1 mm wide, and also demonstrate near-unity internal detection efficiency (IDE) at a wavelength of 4um for a 20um-wide detector--a factor of 20 wider than the current state of the art. This work enables future detectors to overcome the Pearl limit for device width, paving the way for arbitrarily large detectors.
Detecting single photons is essential for applications such as dark matter detection, quantum science and technology, and biomedical imaging. Superconducting nanowire single-photon detectors (SNSPDs) excel in this task due to their near-unity detection efficiency, subhertz dark count rates, and picosecond timing jitter. However, a local increase of current density (current crowding) in the bends of meander-shaped SNSPDs limits these performance metrics. By locally irradiating the SNSPD’s straight segments with helium ions while leaving the bends unirradiated, we realize current crowding–free SNSPDs with simultaneously enhanced sensitivity: After irradiation with 800 ions nm −2 , locally irradiated SNSPDs showed a relative saturation plateau width of 37%, while fully irradiated SNSPDs reached only 10%. This larger relative plateau width allows operation at lower relative bias currents, thereby reducing the dark count rate while still detecting single photons efficiently. We achieve an internal detection efficiency of 94% with 7 mHz dark count rate near the onset of saturating detection efficiency for a wavelength of 780 nm.
Superconducting Nanowire Single-Photon Detectors (SNSPDs) are the premier single-photon counting technology in the near-infrared regime. Operating via a photon-induced phase transition from the superconducting to the normal state, SNSPDs act as highly sensitive digital detectors that now play a critical role in quantum communication, deep-space optical communications, and direct dark matter detection. As the demand for these detectors scales, there is a pressing need to extend their performance capabilities toward longer wavelengths, larger active areas, and higher operating temperatures. However, advancing these metrics requires navigating complex physical trade-offs inherent to the detection mechanism. This thesis explores the material optimizations, novel detector architectures, and fundamental device physics required to push SNSPD technology beyond its current limits. The first thrust of this work focuses on extending SNSPD sensitivity into the mid-infrared (MIR) and far-infrared regimes. By developing a low-Tc (sub-1 K) WSi film engineered to reduce the characteristic detection energy, the threshold for long-wavelength detection is significantly lowered. Coupled with a novel detector architecture utilizing impedance-matching tapers and superconducting nanowire avalanche photon detectors (SNAPs), sensitivity is initially demonstrated at wavelengths up to 29um using a blackbody thermal source. Expanding beyond this limit, the implementation of quantum cascade lasers enables the demonstration of single-photon counting at wavelengths up to 88um, marking a major improvement over the current state of the art. To address the practical MIR detection challenges of low signal-to-noise ratio and restricted fill factors, this work also demonstrates a 1 mm x 1mm array of superconducting microwire single-photon detectors (SMSPDs) sensitive out to 3.7um, establishing a pathway for future antenna-coupled detectors. The second thrust investigates the development of micrometer-scale wires to simultaneously increase active area and operating temperature. Moving to microwire geometries raises fundamental questions regarding intrinsic detection mechanisms. Using a scanning lens setup, this work demonstrates the first direct observation of transverse coordinate effects in microwires, where the precise location of photon incidence across the wire width significantly alters the detector's slew rate and timing performance. To counteract this, new rectification schemes are introduced to produce a more uniform detection landscape. Specifically, the integration of a superconducting rail alongside the main detector is shown to successfully mitigate the transverse coordinate effect, improve timing performance, and increase the viable operating temperature of the detector. The third thrust explores the use of unconventional superconductors, namely MgB2 to achieve an appreciably higher-temperature single-photon detection pathway. This section details the distinct challenges associated with the growth and fabrication of detectors using air-sensitive materials and evaluates their long-term viability for the SNSPD platform. Ultimately, this thesis highlights the critical material and architectural parameters required to advance the field of single-photon detection. By elucidating the metrics and mechanisms that govern ideal detector performance, this work aims to broaden the understanding and future application of SNSPDs across diverse scientific disciplines. All the data presented here is my own unless otherwise mentioned.
Superconducting nanowire single photon detectors (SNSPDs) have demonstrated advantages over traditional detectors in many fields [1]. Most fiber-coupled SNSPDs are coupled to single mode fibers, limiting their usability for applications where large surface area detectors are needed, for example fluorescence detection and satellite-based quantum communication [2][3]. Other important requirements for many applications are broadband detection efficiency, and low timing jitter [4]. So far, the increased meander length of multimode detectors, and the therefore increased kinetic inductance and number of imperfections due to film inhomogeneities have limited the timing jitter [5]. Moreover, combining low timing jitter with high detection efficiency and low dark count rate in one device is challenging due to the tradeoffs between different properties of SNSPDs [6]. In this paper, we achieved high efficiency and strong saturation over a broad wavelength range with a low timing jitter of 16.99 ps while maintaining a low dark count rate of < 0.2 Hz for an SNSPD coupled to a 50 µm core multimode fiber. To enhance the broadband absorption from 405 nm to 830 nm, detectors were fabricated on an optimized SiO2 cavity and Aluminum mirror. The geometry of the nanowire was also tuned to reach a good internal saturation of efficiency over the visible/NIR range but also to carry high current to get a large signal. Furthermore, a cryogenic readout amplifier was optimized to improve the signal to noise ratio and thus lead to high time resolution. Our devices can be readily used to enable higher resolution and faster quantum optics, bio-imaging, laser ranging and other optical experiments.
Abstract Superconducting Nanowire Single-Photon Detectors (SNSPDs) are key building blocks for photonic quantum technologies due to their ability to detect single photons with ultra-high efficiency, low dark counts and fast temporal resolution. Superconducting materials exhibiting high uniformity, large absorption cross-section and atomic-scale thickness are desirable to extend single-photon detection from the near-infrared up to the terahertz regime, where existing material choices are especially constrained. Substrate independence would further open the way to integrating detectors onto functional materials and heterostructures, enhancing performance and enabling proximal readout of a wide range of individual excitations. Here, we pattern the prototypical two-dimensional superconductor niobium diselenide (NbSe 2 ) into few-layer nanowires less than 100 nm wide and demonstrate single-photon detection at 780 nm and 1550 nm. At the same time, the dark-count rate remains below 1 Hz up to the switching current and we achieve a timing jitter below 50 ps. We estimate via a diffusive hot-spot model that materials and geometric parameters would allow a theoretical cut-off wavelength in the millimetre range, assuming state-of-the-art device parameters. Our results open up routes toward quantum-limited detectors integrated into quantum-photonic circuits and quantum devices, with the potential for novel detection capabilities and unprecedented energy sensitivity.
Superconducting nanowire single-photon detectors (SNSPDs) provide high efficiency for detecting individual photons while keeping dark counts and timing jitter minimal. Besides superior detection performance over a broad optical bandwidth, compatibility with an integrated optical platform is a crucial requirement for applications in emerging quantum photonic technologies. Here we present SNSPDs embedded in nanophotonic integrated circuits which achieve internal quantum efficiencies close to unity at 1550 nm wavelength. This allows for the SNSPDs to be operated at bias currents far below the critical current where unwanted dark count events reach milli-Hz levels while on-chip detection efficiencies above 70% are maintained. The measured dark count rates correspond to noise-equivalent powers in the 10(-19) W/Hz(-1/2) range and the timing jitter is as low as 35 ps. Our detectors are fully scalable and interface directly with waveguide-based optical platforms.