Collective Subradiance Advances Sensing Beyond Heisenberg Limit with N² Figure of Merit
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The pursuit of increasingly precise measurements drives innovation across many scientific fields, and researchers continually seek ways to overcome fundamental limits to sensitivity. Xin Wang and Zeyang Liao, both from Sun Yat-sen University, alongside their colleagues, now demonstrate a pathway to surpass these limitations using carefully arranged collections of light-emitting atoms. Their work explores how strong interactions between these atoms, when coupled to a nanoscale waveguide, create a unique collective behaviour known as subradiance, resulting in exceptionally narrow resonances. This allows for the detection of incredibly small changes, potentially enabling sensors with a precision that scales favourably, and represents a significant step towards building highly sensitive, scalable devices on integrated nanophotonic platforms. Analysis of the effective non-Hermitian Hamiltonian reveals a universal scaling law for the decay rate of the most subradiant state, which exhibits an N−3 scaling with oscillatory behaviour in the deep-subwavelength regime. This scaling is directly observable in the single-photon scattering spectrum, enabling the detection of minute changes in atomic separation with a figure of merit that scales as N. The quantum Fisher information scales as N6 and can be closely approached by measuring spectral shifts near the steepest slope of the most subradiant resonance. These enhancements remain robust under realistic positional disorder, confirming that dipole-dipole-engineered subradiant states offer a pathway to precision metrology. Subradiant Resonances and Emitter Array Sensitivity Scientists engineered a system to explore the metrological potential of subwavelength-spaced emitter arrays coupled to a one-dimensional nanophotonic waveguide, focusing on the emergence of ultranarrow subradiant resonances resulting from strong dipole-dipole interactions. The study pioneered an eigenmode analysis using a non-Hermitian Hamiltonian to derive a universal scaling law governing the decay rate of the most subradiant state, revealing oscillatory behaviour in the deep-subwavelength regime. This scaling was directly observed in single-photon scattering spectra, enabling the detection of minute changes in atomic separation. To quantify sensitivity, researchers calculated the Fisher information, which scales as N6, and demonstrated that this value could be closely approached by measuring spectral shifts near the steepest slope of the most subradiant resonance.
The team meticulously investigated the robustness of these enhancements under realistic positional disorder, confirming that dipole-dipole-engineered subradiance provides a viable resource for high-precision sensing. Experiments employed a carefully constructed system where emitter arrays were positioned at subwavelength distances, ensuring strong coupling to the nanophotonic waveguide and maximizing the impact of dipole-dipole interactions on the collective response. The study harnessed single-photon scattering to probe the spectral characteristics of the subradiant resonances, allowing for precise measurements of the decay rates and identification of the oscillatory scaling behaviour. Scientists developed a method to analyze the resulting spectra, extracting the Fisher information and quantifying the sensitivity of the system to changes in atomic separation. This approach enables the creation of scalable sensors on integrated nanophotonic platforms, opening new avenues for high-precision metrology and quantum sensing applications.
The team’s work bridges many-body waveguide electrodynamics and high-precision sensing, demonstrating a pathway toward advanced sensor technologies. Waveguide QED and Atomic Array Interactions This body of research focuses on quantum optics, waveguide quantum electrodynamics (QED), and related areas. The core theme is the interaction of light with matter confined within one-dimensional waveguides, a key area for building quantum networks and processing information. A significant portion of the work explores arrays of atoms interacting with light, focusing on phenomena like subradiance, where atoms cooperate to slow down light emission, leading to long-lived excitations and enhanced light-matter interaction. Collective excitations, describing how atoms collectively respond to light, and the dynamics of these excitations in small and large arrays are also central to this research. Several studies highlight the use of these systems for precise measurements, leveraging quantum properties to achieve higher precision than classical methods. The research also aims at building quantum networks, investigating photon storage and retrieval, single-photon sources and detectors, and quantum repeaters. A growing trend is integrating these quantum systems with diamond-based nanophotonic structures, utilizing colour centres in diamond as excellent qubits with long coherence times. The research encompasses theoretical foundations of waveguide QED and collective effects, experimental implementations, and materials science, demonstrating a strong push towards practical quantum technologies. Chang, K. Mølmer, M. S. Zubairy, and Z. Liao, who have made significant contributions to the theoretical and experimental understanding of these systems. The overall impression is that this research represents a current and comprehensive overview of a rapidly evolving field, driving progress towards realizing quantum networks, sensors, and processors.
Atomic Arrays Enhance Measurement Sensitivity Dramatically This research demonstrates a pathway to significantly enhance the precision of measurements by harnessing the collective behaviour of closely spaced atoms interacting with light within a nanophotonic waveguide.
Scientists have shown that by carefully arranging these atoms, strong interactions emerge, creating what are known as subradiant resonances, which exhibit exceptionally narrow spectral features. Through detailed analysis, the team derived a universal scaling law governing the decay rate of the most subradiant state, revealing its dependence on the number of atoms in the array. The findings demonstrate that the sensitivity of these atomic arrays to changes in their environment, such as minute shifts in spacing, increases dramatically with the number of atoms, scaling as N3 for the figure of merit and N6 for the quantum Fisher information. This enhancement surpasses the standard quantum limit, offering the potential to detect displacements on the order of 10−12 λ, where λ represents the wavelength of light. Importantly, the researchers established that these favourable scaling laws remain robust even when the atoms are not perfectly positioned, suggesting practical viability for real-world applications. This work paves the way for developing compact, noise-resistant, and highly sensitive quantum sensors integrated on nanophotonic platforms. The authors acknowledge that achieving these levels of precision requires suppressing various sources of noise, including thermal fluctuations. Future research will likely focus on further mitigating these noise sources and exploring different materials and configurations to optimize the performance of these quantum sensors.
The team also intends to investigate the potential of this approach for applications beyond metrology, such as quantum information processing and fundamental tests of physics. 👉 More information 🗞 Super-Heisenberg-limited Sensing via Collective Subradiance in Waveguide QED 🧠 ArXiv: https://arxiv.org/abs/2512.14463 Tags: