In a groundbreaking advancement at the forefront of quantum photonics, researchers at The City College of New York have unveiled novel interactions between quantum emitters and tailor-made photonic structures, opening new pathways for on-chip quantum information processing. Led by Carlos A. Meriles, Professor of Physics, the team’s experimental exploration centers on the nitrogen-vacancy (NV) center in diamond, an atomic-scale defect known for generating photons with remarkable quantum properties. Their findings demonstrate how the NV center’s inherently broad emission spectrum, once considered a nuisance, can be harnessed through engineered topological photonic waveguide modes to achieve unprecedented control over light–matter interactions.
The NV center, a point defect where a nitrogen impurity sits adjacent to a vacant site within diamond’s crystal lattice, serves as a natural quantum emitter whose spin states can be manipulated via optical and microwave excitation. It possesses remarkable capabilities for quantum sensing and communication, largely due to its long coherence times and stable spin-dependent fluorescence. Nevertheless, the NV center’s photoluminescence typically exhibits a broad and complex emission profile spanning multiple wavelengths, posing challenges for spectral indistinguishability and integration with photonic circuitry. The City College team, however, leveraged this characteristic in an ingenious way, revamping a supposed disadvantage into an advantage by coupling the NV emission to specially designed topological photonic waveguides.
Topological photonics has emerged as a vibrant field that exploits concepts from topological insulators in condensed matter physics to create photonic structures exhibiting robust, defect-immune modes. These modes propagate along edges or interfaces without backscattering, even in the presence of imperfections, thereby promising highly efficient and stable photon transport. By integrating NV-hosting nanodiamonds onto atomic force microscope (AFM) tips, the researchers developed a unique scanning probe methodology that permits spatially resolved interaction studies between the emitter and the photonic architecture. The AFM tip serves not only to position the quantum emitter with nanoscale precision but also to interrogate local photonic modes by analyzing emitted photons’ spectral and polarization properties.
A remarkable aspect of this investigation is the application of polarization-resolved spectroscopy to decode the complex interplay between the NV center’s emission and the underlying topological waveguide modes. Through suppression of right circularly polarized (RCP) emission at 710 nm—a key wavelength associated with the NV center’s zero-phonon line and phonon sideband—the team mapped regions supporting chiral photonic modes, manifesting as distinctive intensity fringes. This selective filtering unveiled spatial patterns within the waveguide’s electromagnetic environment that are intimately connected to the underlying topological properties, revealing domains where light fields exhibit one-way propagation determined by their handedness.
The implications of coupling the broad-band NV emission with topological photonic modes resonate deeply within quantum technology realms. Traditional efforts to generate deterministic single-photon sources with narrow linewidths often struggle with spectral diffusion and decoherence. By contrast, the demonstrated topological shaping of NV emission suggests avenues to mitigate these effects, potentially stabilizing photon frequencies and enabling robust spin–photon entanglement essential for quantum networks. Furthermore, the robustness of chiral photonic modes against scattering and fabrication imperfections indicates practical advantages in constructing scalable, integrated quantum optical circuits capable of maintaining coherence over extended distances.
Beyond quantum information processing, the team’s work pioneers a new, highly sensitive form of nanoscale sensing. The polarization sensitivity inherent in their approach permits reconstruction of photonic mode distributions with exceptional contrast, enabling detailed imaging of electromagnetic fields at the nanoscale. This methodology extends the capabilities of NV centers beyond traditional magnetometry or thermometry, positioning them as versatile probes for assessing the complex local photonic environment with both spatial and polarization resolution. Such advanced imaging capabilities could accelerate progress in nanophotonics, optical metamaterials, and biosensing.
At the interface of physics and biology, the polarization-resolved approach to detecting chiral photonic modes hints at transformative applications in molecular sensing. Chiral molecules, ubiquitous in living organisms and pharmaceuticals, often evade detection through conventional techniques due to subtle optical activity signatures. The researchers anticipate that adapting their method might enable direct sensing and characterization of molecular chirality with heightened sensitivity and spatial resolution, providing crucial insights into biomolecular structures and interactions. This integration of quantum photonics and molecular spectroscopy promises a fertile domain for future interdisciplinary research.
Follow-up investigations are set to delve deeper into the fundamental physics governing emitter–structure interactions and to push technological boundaries for device implementation. Optimization efforts will target enhancing the coupling efficiency between NV centers and topological waveguides, improving the spatial precision of emission control, and extending the approach to other quantum emitters and wavelength ranges. The synergy between experimental innovation and theoretical modeling will illuminate mechanisms underlying chiral emission, spontaneous emission modulation, and photon routing, fueling the design of next-generation photonic devices.
The versatility of the AFM-nanodiamond scanning probe technique also opens avenues for exploring a wide array of engineered photonic environments, including those with dynamically tunable topologies or nontrivial quantum properties. Researchers envision employing this platform to investigate photon-mediated spin interactions, coherent spin–spin coupling, and nonreciprocal light–matter phenomena crucial for quantum computation and secure communication. Such comprehensive studies promise to bridge gaps between fundamental quantum science and practical device engineering.
This work epitomizes a shift in quantum nanophotonics: transforming broad emission spectra from a limitation into a resource for advanced quantum control. The convergence of topological concepts with quantum emitter technology signifies a forward-looking paradigm wherein robust, defect-immune photonic states can harness complex quantum phenomena for real-world applications. As the field evolves, the City College team’s achievements mark a significant milestone, underscoring the power of interdisciplinary approaches to solve longstanding challenges in quantum engineering.
In sum, the research by Professor Carlos Meriles and collaborators provides profound insights into manipulating nitrogen-vacancy centers within topological photonic architectures. By meticulously coupling the NV center emission with chiral, topologically protected modes and employing nanoscale scanning probes, the team has charted a novel landscape where quantum emitters and advanced photonic materials coalesce. This synergy holds promise not only for enhancing quantum information technologies but also for innovating nanoscale sensing tools with far-reaching implications in medicine, materials science, and beyond.
The publication, appearing in the prestigious journal Nature Nanotechnology, highlights experimental advances accomplished through rigorous spectroscopy, nanofabrication, and probe scanning methodologies. As quantum photonics continues to steer toward integrated on-chip solutions, the principles and techniques established by this study will likely influence a broad spectrum of future research, catalyzing innovations that harness the nuanced interplay between quantum defects and engineered light.
Subject of Research: Not applicable
Article Title: Emission of Nitrogen–Vacancy Centres in Diamond Shaped by Topological Photonic Waveguide Mode
News Publication Date: 28-Aug-2025
Image Credits: Carlos Meriles
Keywords
Nitrogen-vacancy center, quantum emitter, topological photonics, chiral photonic modes, nanodiamond, scanning probe microscopy, quantum information, spin–photon entanglement, nanoscale sensing, polarization-resolved spectroscopy, quantum coherence, integrated photonic circuits
Tags: broad emission spectrum challengesCarlos A. Meriles quantum researchCCNY physics research breakthroughsengineered topological photonic waveguide modeslight-matter interactions controlnitrogen-vacancy center researchon-chip quantum information processingphotonic circuitry integrationquantum emitters in diamondsquantum photonics advancementsquantum sensing and communicationspin states manipulation in quantum systems
