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arXiv:2511.01279

Super-resolved reconstruction of single-photon emitter locations from $g^{(2)}(0)$ maps

Sonali Gupta, Amit Kumar, Vikas S Bhat, Sushil Mujumdar

quant-phphysics.opticsSubmitted Nov 3, 2025• Announced Nov 4, 2025• 0 citations• Revised Apr 12, 2026 (v2)
v1 · Nov 3, 2025v2 · Apr 12, 2026
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Abstract

Single-photon sources are vital for emerging quantum technologies. In particular, Nitrogen-vacancy (NV) centers in diamond are promising due to their room-temperature stability, long spin coherence, and compatibility with nanophotonic structures. A key challenge, however, is the reliable identification of isolated NV centers, since conventional confocal microscopy is diffraction-limited and cannot resolve emitter distributions within a focal spot. Besides, the associated intensity scanning is a time-expensive procedure. Here, we introduce a raster-scanned $g^{(2)}(0)$ mapping technique combined with an inversion-based reconstruction algorithm. By directly measuring local photon antibunching across the field of view, we extract the effective emitter number within each focal spot and reconstruct occupancy maps on a sub-focal-spot grid. This enables recovery of the number and spatial distribution of emitters within regions smaller than the confocal focal spot, thereby offering possibilities of going beyond the diffraction limit. Our simulations confirm robust reconstruction of NV-center distributions. The method provides a practical diagnostic tool for locating single-photon sources in an efficient and accurate manner, at much lesser time and effort compared to conventional intensity scanning. It offers valuable feedback for nanophotonic device fabrication, supporting more precise and scalable integration of NV-based quantum photonic technologies.

Comments
22 pages, 6 figures

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Super-resolved reconstruction of single-photon emitter locations from g(2)(0)g^{(2)}(0)g(2)(0) maps
Single-photon sources are vital for emerging quantum technologies. In particular, Nitrogen-vacancy (NV) centers in diamond are promising due to their room-temperature stability, long spin coherence, and compatibility with nanophotonic structures. A key challenge, however, is the reliable identification of isolated NV centers, since conventional confocal microscopy is diffraction-limited and cannot resolve emitter distributions within a focal spot. Besides, the associated intensity scanning is a time-expensive procedure. Here, we introduce a raster-scanned g(2)(0)g^{(2)}(0)g(2)(0) mapping technique combined with an inversion-based reconstruction algorithm. By directly measuring local photon antibunching across the field of view, we extract the effective emitter number within each focal spot and reconstruct occupancy maps on a sub-focal-spot grid. This enables recovery of the number and spatial distribution of emitters within regions smaller than the confocal focal spot, thereby offering possibilities of going beyond the diffraction limit. Our simulations confirm robust reconstruction of NV-center distributions. The method provides a practical diagnostic tool for locating single-photon sources in an efficient and accurate manner, at much lesser time and effort compared to conventional intensity scanning. It offers valuable feedback for nanophotonic device fabrication, supporting more precise and scalable integration of NV-based quantum photonic technologies.
Single-photon sources are vital for emerging quantum technologies. In particular, Nitrogen-vacancy (NV) centers in diamond are promising due to their room-temperature stability, long spin coherence, and compatibility with nanophotonic structures. A key challenge, however, is the reliable identification of isolated NV centers, since conventional confocal microscopy is diffraction-limited and cannot resolve emitter distributions within a focal spot. Besides, the associated intensity scanning is a time-expensive procedure. Here, we introduce a simulation-based raster-scanned g ( 2 ) ( 0 ) mapping technique combined with an inversion-based reconstruction algorithm. Using synthetically generated photon-timestamp data for randomly distributed NV centers under a scanned Gaussian excitation profile, by directly measuring local photon antibunching across the field of view, we extract the effective emitter number within each focal spot and reconstruct occupancy maps on a sub-focal-spot grid. This enables recovery of the number and spatial distribution of emitters within regions smaller than the confocal focal spot, thereby offering possibilities of going beyond the diffraction limit. Simulations confirm robust reconstruction of NV-center distributions. The method reduces experimental effort in identifying isolated emitters by inferring the effective emitter number and sub-diffraction occupancy within each focal spot in a single scan, thereby avoiding unnecessary searches in regions that do not contain single emitters, as commonly encountered in intensity-based scanning approaches. It offers valuable feedback for nanophotonic device fabrication, supporting more precise and scalable integration of NV-based quantum photonic technologies.
Optical imaging of quantum emitters is essential for a wide range of quantum applications. Conventional confocal imaging relies on point-by-point raster scanning, which is inherently time-consuming and photon-inefficient, particularly for sparse emitter distributions and photon-limited samples. Here, we demonstrate a compressive sensing-based imaging approach, where spatially structured wide-field excitation replaces raster scanning, enabling reconstruction of sparse emitters. In our implementation, random binary patterns are used to acquire compressive measurements, from which the spatial fluorescence distribution is reconstructed using a GPSR-BB algorithm. We experimentally demonstrate this approach using nitrogen-vacancy (NV) centers in diamond as a representative platform, with high-fidelity image reconstruction achieved using only approximately 20%20\%20% of the measurements required for conventional raster scanning. In addition to intensity reconstruction, we extend this framework to reconstruct spatial maps of the second-order correlation function g(2)(0)g^{(2)}(0)g(2)(0) from compressive measurements. This enables identification of single-photon emitters through antibunching signatures using significantly reduced data.
Optical imaging of quantum emitters is essential for a wide range of quantum applications. Conventional confocal imaging relies on point-by-point raster scanning, which is inherently time-consuming, particularly for sparse emitter distributions and photon-limited samples. Here, we demonstrate a compressive-sensing-based fluorescence imaging approach in which spatially structured wide-field excitation is used to acquire multiplexed measurements of sparse emitters. In our implementation, random binary patterns are projected onto the sample, and the spatial fluorescence distribution is reconstructed from the measured signals using a gradient projection for a sparse reconstruction algorithm with Barzilai Borwein step size (GPSR-BB). We experimentally demonstrate this approach using nitrogen-vacancy (NV) centers in diamond as a representative platform, achieving high-fidelity image reconstruction using only approximately 20% of the measurements required for conventional raster scanning. Beyond intensity reconstruction, we develop a compressive correlation-reconstruction model for recovering spatial maps of the second-order correlation function g (2) (0) from photon-correlation measurements. Through numerical simulations, we show that the reconstructed g (2) (0) maps can identify single-photon-emitter locations using the antibunching criterion g (2) (0) < 0.5. These results demonstrate that compressive sampling can reduce measurement overhead while preserving spatial information and enabling correlation-based quantum-emitter identification.
Single-photon sources are essential for quantum technologies, supporting secure communication, quantum computing, and integrated photonic systems. Nitrogen-vacancy (NV) centers in nanodiamonds are robust emitters that operate at room temperature and can be positioned on-chip, but efficient coupling to photonic modes remains challenging. We present the design, fabrication, and experimental characterization of a silicon nitride photonic structure engineered to enhance and extract emission from NV centers. The device features a subwavelength gap between waveguides, a Bragg reflector for emission redirection, and an output waveguide for collection. Simulations guided the optimization of the geometry to increase the spontaneous emission rate through photonic confinement. Nanodiamonds were deposited into the gap using lithographic patterning and drop-casting. Fluorescence lifetime measurements confirm that the structure modifies the emission dynamics of the NV centers. The approach is compatible with scalable fabrication techniques and offers a practical route toward integrated, chip-based single-photon sources.
Nitrogen-vacancy (NV) centers in nanodiamond are photostable single photon emitters at room temperature and are considered to be promising candidates for integrated nanophotonics and quantum information processing. A successful implementation of NV centers in nanophotonic devices requires knowledge about the photophysical properties of each emitter such as brightness, decay rate and quantum efficiency. Recent reports show that not all NV centers in diamond nanocrystals are identical and indeed show distributions in brightness and decay rate [1,2]. Here, we report on experimental quantification of the quantum efficiency (QE) of individual nanodiamonds containing single NV centers. Additionally, we report on measurements of decay rate and brightness of single nanodiamond NV centers and discuss if/which NV centers are suitable emitters to be integrated in nanophotonic devices.
The nitrogen vacancy center in diamond in its negative charge state is a promising candidate for quantum optic experiments that require single photon emitters. Important benefits of the NV center are its high brightness and photo-stability, even at room temperature. Engineering the emission properties of NV centers with optical resonators is a widely followed approach to meet the requirements for quantum technological applications, but the effect on non-radiative decay paths is yet to be understood. Here we report on modifying the internal quantum efficiency of a single NV center in a nanodiamond coupled to a 1D photonic crystal cavity. We assess the Purcell enhancement via three independent measurement techniques and perform autocorrelation measurements at elevated excitation powers in confocal microscopy. Employing a three-level model allows us to extract the setup efficiency, individual transition rates and thus the internal quantum efficiency of our system. Combining our results, we find that the enhancement of the radiative decay rate via the Purcell effect results in an internal quantum efficiency of 90 % for cavity-coupled NV centers. Our findings will facilitate the realization of nano-scale single photon sources with near-unity internal quantum efficiencies operating at high repetition rates.