Single-photon emitters (SPEs) are essential building blocks for quantum photonics. In recent decades, numerous solid-state SPEs have been discovered, offering emission across various wavelengths and operating conditions, and showing great potential for scalable quantum photonic platforms. However, realizing large-scale applications requires efficient and high-throughput characterization, which remains insufficiently explored.Here, we present a quantum microscope, which is a universal platform compatible with the investigation of different types of solid-state SPEs. By integrating super- conducting nanowire single-photon detectors (SNSPDs), our system enables precise photon counting and reliable identification of individual emitters. Using this platform, we demonstrate measurements on both defects in hexagonal boron nitride (hBN) and semiconductor quantum dots, showcasing its adaptability across material systems. We further discuss methods to improve measurement efficiency, including a machine learning classifier that accelerates the selection of SPEs based on second-order auto- correlation measurements. Our work provides a versatile platform for large-scale and efficient characterization of solid-state single-photon emitters, thereby advancing the development of scalable quantum photonic systems.
Single-photon emitters (SPEs) are essential building blocks for quantum photonics. In recent decades, numerous solid-state SPEs have been discovered, offering emission across various wavelengths and operating conditions, and showing great potential for scalable quantum photonic platforms. However, realizing large-scale applications requires efficient and high-throughput characterization, which remains insufficiently explored.Here, we present a quantum microscope, which is a universal platform compatible with the investigation of different types of solid-state SPEs. By integrating super- conducting nanowire single-photon detectors (SNSPDs), our system enables precise photon counting and reliable identification of individual emitters. Using this platform, we demonstrate measurements on both defects in hexagonal boron nitride (hBN) and semiconductor quantum dots, showcasing its adaptability across material systems. We further discuss methods to improve measurement efficiency, including a machine learning classifier that accelerates the selection of SPEs based on second-order auto- correlation measurements. Our work provides a versatile platform for large-scale and efficient characterization of solid-state single-photon emitters, thereby advancing the development of scalable quantum photonic systems.
Single-photon emitters (SPEs) constitute a foundational resource for quantum technologies, including secure communication, photonic quantum computing, and emerging quantum network architectures. A wide range of quantum materials, from atom-like point defects in bulk crystals to excitonic states in low-dimensional semiconductors, now provide bright, coherent, and scalable sources of non-classical light. Meanwhile, advances in photonic integration have enabled efficient routing, filtering, and on-chip manipulation of these emitters. From this perspective, we survey and discuss the technological landscape in which solid-state emitters interface with quantum sensing, quantum communication, quantum computation, and emerging photonic AI platforms. Further, we discuss the materials landscape underpinning modern single-photon sources from the zero-dimensional, one-dimensional, two-dimensional and three-dimensional materials. Lastly, we highlight key integration pathways for these single-photon emitters into scalable quantum photonic systems.
Abstract Single-photon emitters (SPEs) constitute a foundational resource for quantum technologies, including secure communication, photonic quantum computing, and emerging quantum network architectures. A wide range of quantum materials, from atom-like point defects in bulk crystals to excitonic states in low-dimensional semiconductors, now provide bright, coherent, and scalable sources of non-classical light. Meanwhile, advances in photonic integration have enabled efficient routing, filtering, and on-chip manipulation of these emitters. From this perspective, we survey and discuss the technological landscape in which solid-state emitters interface with quantum sensing, quantum communication, quantum computation, and emerging photonic artificial intelligence platforms. Further, we discuss the materials landscape underpinning modern single-photon sources from the zero-dimensional, one-dimensional, two-dimensional and three-dimensional materials. Lastly, we highlight key integration pathways for these SPEs into scalable quantum photonic systems.
Superconducting nanowire single-photon detectors (SNSPDs) are renowned for their high detection efficiency, low dark count rate, and fast timing resolution, which have emerged as an essential device in quantum technologies, including quantum computing and communication, which also significantly benefits classical applications such as deep-space communication, neuromorphic computing, and light detection and ranging (LiDAR). However, designing and customizing SNSPD into versatile functionalities to satisfy these intensive requirements poses significant challenges, including thin-film deposition, nanofabrication, electrical integration, and light delivery strategies. While prior work has typically optimized individual steps – such as fabrication or characterization – there is a lack of reported systematic, integrated frameworks that span all stages from device design to performance benchmarking. This gap hinders broader adoption of the technology across scientific and industrial communities and limits the rigorous exploration of advanced detection concepts. This thesis aims to establish an end-to-end workflow for the customizable fabrication and comprehensive characterization of superconducting nanowire single-photon detectors, and to demonstrate that such a platform is essential for the investigation of diverse single-photon detection architectures. It begins with the optimization of NbTiN thin-film deposition utilizing an ultrahigh vacuum sputtering system. By systematically identifying and optimizing key deposition parameters, we achieve NbTiN films with targeted superconducting properties along with high uniformity and reproducibility. This fast and reliable workflow establishes a solid foundation for detector fabrication and provides instructions for flexible control over film properties. Furthermore, effective nanofabrication protocols for the high-quality SNSPDs were elaborated, along with the specialized cryogenic packaging techniques for reliable electrical and optical integration. The achieved devices demonstrated performance metrics comparable to commercial systems. The implementation of this full fabrication—characterization cycle also enabled flexible exploration of advanced detector architectures. For example, we investigated superconducting microbridge single-photon detectors (SMSPDs) as a complementary platform, demonstrating a fivefold enhancement in signal-to-noise ratio and a tenfold reduction in recovery time relative to conventional SNSPDs. These results provide quantitative insight into detector design trade-offs. Within this framework, photon-number-resolving (PNR) detection using SNSPDs was further investigated as an essential function for advanced quantum and classical applications. We presented innovative detector architectures—interleaved multi-pixel arrays and multilayer coherent absorption structures—to overcome limitations inherent in conventional multiplexing methods, such as nonuniform detection, temporal degradation, and crosstalk. An interleaved multi-pixel SNSPD array with up to four-photon resolution was achieved with uniform detection, as well as a multilayer architecture based on coherent absorption with uniform and near-unity absorption efficiency. Importantly, a theoretical comparison between these two architectures was conducted to evaluate their absorption efficiency and PNR performance, offering insights into structural optimization and device scalability for advanced PNR detectors. Overall, this thesis establishes a fully in-house SNSPD fabrication and characterization capability, providing a robust foundation for the development, customization, and evaluation of high-performance superconducting single-photon detectors. This platform enables reproducible design optimization, quantitative performance benchmarking, and systematic exploration of detector architectures. By integrating fabrication, characterization, and architectural innovation within a consistent workflow, it facilitates both fundamental investigation and application-driven advancement of single-photon detection technologies in our laboratory and the broader research community in Singapore.
Photonic integrated quantum circuits could fully unlock quantum systems' potential. However,monololithic platforms face several challenges. We explore hybrid quantum photonic integration, combining different photonic materials to mitigate monolithic approaches disadvantages . Our work introduces hybrid circuits integrating different quantum sources and materials. We present a technique integrating nanowire single photon sources with silicon nitride waveguides, enabling circuit reconfiguration and emission wavelength control using heat, and strain tuning which is compatible with superconducting single photon detectors . We realize a full quantum transceiver on chip using on demand single photon sources and SNSPDS, in additio to dispersion engineering of superconducting transmission lines for SNSPDs multi-pixel integration. We discuss progress towards room-temperature quantum integrated photonics using hexagonal boron nitride quantum emitters. Finally, we delve into scalable generation and quantum state reconstruction of W-states and construction using phase retrieval algorithms, and ongoing research on topological photonics, and photonic lattices.
Solid-state quantum emitters coupled to integrated photonic nanostructures are quintessential for exploring fundamental phenomena in cavity quantum electrodynamics and widely employed in photonic quantum technologies such as non-classical light sources, quantum repeaters, and quantum transducers, etc. One of the most exciting promises from integrated quantum photonics is the potential of scalability that enables massive productions of miniaturized devices on a single chip. In reality, the yield of efficient and reproducible light-matter couplings is greatly hindered by the spectral and spatial mismatches between the single solid-state quantum emitters and confined or propagating optical modes supported by the photonic nanostructures, preventing the high-throughput realization of large-scale integrated quantum photonic circuits for more advanced quantum information processing tasks. In this work, we introduce the concept of hyperspectral imaging in quantum optics, for the first time, to address such a long-standing issue. By exploiting the extended mode with a unique dispersion in a 1D planar cavity, the spectral and spatial information of each individual quantum dot in an ensemble can be accurately and reliably extracted from a single wide-field photoluminescence image with super-resolutions. With the extracted quantum dot positions and emission wavelengths, surface-emitting quantum light sources and in-plane photonic circuits can be deterministically fabricated with a high-throughput by etching the 1D confined planar cavity into 3D confined micropillars and 2D confined waveguides. Further extension of this technique by employing an open planar cavity could be exploited for pursuing a variety of compact quantum photonic devices with expanded functionalities for large-scale integration. Our work is expected to change the landscape of integrated quantum photonic technology.
A broad range of scientific and industrial disciplines require precise optical measurements at very low light levels. Single-photon detectors combining high efficiency and high time resolution are pivotal in such experiments. By using relatively thick films of NbTiN (8-11\,nm) and improving the pattern fidelity of the nano-structure of the superconducting nanowire single-photon detectors (SNSPD), we fabricated devices demonstrating superior performance over all previously reported detectors in the combination of efficiency and time resolution. Our findings prove that small variations in the nanowire width, in the order of a few nanometers, can lead to a significant penalty on their temporal response. Addressing these issues, we consistently achieved high time resolution (best device 7.7\,ps, other devices $\sim$10-16\,ps) simultaneously with high system detection efficiencies (80−90%) in the wavelength range of 780-1000\,nm, as well as in the telecom bands (1310-1550\,nm). The use of thicker films allowed us to fabricate large-area multi-pixel devices with homogeneous pixel performance. We first fabricated and characterized a 100×100μm2 16-pixel detector and showed there was little variation among individual pixels. Additionally, to showcase the power of our platform, we fabricated and characterized 4-pixel multimode fiber-coupled detectors and carried out photon correlation experiments on a nanowire quantum dot resulting in g2(0) values lower than 0.04. The multi-pixel detectors alleviate the need for beamsplitters and can be used for higher order correlations with promising prospects not only in the field of quantum optics, but also in bio-imaging applications, such as fluorescence microscopy and positron emission tomography.