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arXiv:2504.10815 · npj Quantum Information

Room-temperature hybrid 2D-3D quantum spin system for enhanced magnetic sensing and many-body dynamics

Haoyu Sun, Pei Yu, Xu Zhou, Xiangyu Ye, Mengqi Wang, Zhaoxin Liu, Yuhang Guo, Wen‐Zhao Liu, You Huang, Pengfei Wang, Fazhan Shi, Kangwei Xia, Ya Wang

Published Dec 6, 2025• 2 citations
arXivHTMLPDF

Abstract

Abstract Advances in hybrid quantum systems and their precise control are pivotal for developing advanced quantum technologies. Two-dimensional (2D) materials with optically accessible spin defects have emerged as a promising platform for building integrated quantum spin systems due to their exceptional flexibility and scalability. However, experimentally realizing such systems and demonstrating their superiority remains challenging. Here, we present a hybrid spin system operating under ambient conditions, integrating boron vacancy ( $${{\rm{V}}}_{{\rm{B}}}^{-}$$ V B − ) spins in 2D hexagonal boron nitride flakes with a single nitrogen vacancy (NV) center in 3D single-crystal diamonds. This combined system achieves full controllability and exhibits enhanced performance for nanoscale magnetic sensing, including an improved dynamic range. Moreover, we investigate the rich many-body spin dynamics within the hybrid system, which enables us to estimate the concentration of $${{\rm{V}}}_{{\rm{B}}}^{-}$$ V B − spins. This work provides a critical foundation for advancing the development of 2D-3D integrated quantum spin systems.

DOI
10.1038/s41534-025-01152-4

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Abstract Advances in hybrid quantum systems and their precise control are pivotal for developing advanced quantum technologies. Two-dimensional (2D) materials with optically accessible spin defects have emerged as a promising platform for building integrated quantum spin systems due to their exceptional flexibility and scalability. However, experimentally realizing such systems and demonstrating their superiority remains challenging. Here, we present a hybrid spin system operating under ambient conditions, integrating boron vacancy ( VB−{{\rm{V}}}_{{\rm{B}}}^{-}VB−​ V B − ) spins in 2D hexagonal boron nitride flakes with a single nitrogen vacancy (NV) center in 3D single-crystal diamonds. This combined system achieves full controllability and exhibits enhanced performance for nanoscale magnetic sensing, including an improved dynamic range. Moreover, we investigate the rich many-body spin dynamics within the hybrid system, which enables us to estimate the concentration of VB−{{\rm{V}}}_{{\rm{B}}}^{-}VB−​ V B − spins. This work provides a critical foundation for advancing the development of 2D-3D integrated quantum spin systems.
Emergent phenomena in interacting quantum systems arise from collective behavior that cannot be reduced to single-particle physics. Understanding these phenomena requires platforms capable of both synthesizing many-body states under controlled conditions and probing them at the microscopic scale where correlations originate. Solid-state spin defects, including nitrogen-vacancy (NV) centers in diamond and negatively charged boron vacancy centers in hexagonal boron nitride (hBN), offer precisely this dual capability. In the first part of this dissertation, a strongly interacting NV ensemble is subjected to periodic and quasi-periodic drives to access a long-lived prethermal regime and realize a discrete time quasicrystal (DTQC). In the second part, the boron vacancy center in hBN is developed as a two-dimensional quantum sensor through coherence characterization and isotope engineering, then deployed inside a diamond anvil cell to image stress and magnetism simultaneously at gigapascal pressures, resolving a pressure-induced magnetic phase transition in a Cr1+δ_{1+\delta}1+δ​Te2_22​/hBN heterostructure. Moreover, NV scanning cross-relaxometry enables nanoscale mapping of spin defects in hBN, while noise spectroscopy is applied to probe superconducting fluctuations and vortex dynamics in a cuprate thin film. Together, these results demonstrate that solid-state spins provide a versatile experimental framework in which quantum simulation, sensor development, and materials characterization inform and reinforce one another.
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Negatively charged boron vacancy (VB−\mathrm{V_B^-}VB−​) in hexagonal boron nitride (hBN) is the most extensively studied room-temperature quantum spin system in two-dimensional (2D) materials. Nevertheless, the current effective readout of VB−\mathrm{V_B^-}VB−​ spin states is carried out by systematically optical methods. This limits their exploitation in compact and miniaturized quantum devices, which would otherwise hold substantial promise to address quantum sensing and quantum information tasks. In this study, we demonstrated a photoelectric spin readout technique for VB−\mathrm{V_B^-}VB−​ spins in hBN. The observed photocurrent signals stem from the spin-dependent ionization dynamics of boron vacancies, mediated by spin-dependent non-radiative transitions to a metastable state. We further extend this electrical detection technique to enable the readout of dynamical decoupling sequences, including the Carr-Purcell-Meiboom-Gill (CPMG) protocols, and of nuclear spins via electron-nuclear double resonance. These results provide a pathway toward on-chip integration and real-field exploitation of quantum functionalities based on 2D material platforms.
Solid-state spin defects, particularly the nitrogen-vacancy (NV) center in diamond, have emerged as powerful platforms for exploring quantum many-body physics and quantum metrology. Their exceptional coherence properties and strong dipolar interactions offer unique opportunities to simulate complex quantum dynamics and engineer entangled states for enhanced sensing beyond the standard quantum limit. However, achieving scalable entanglement in these systems is notoriously difficult due to intrinsic disorder and the complex nature of long-range dipole-dipole interactions. This thesis presents both theoretical and experimental advancements in harnessing quantum dynamics in interacting spin ensembles for quantum-enhanced metrology. A central result is the experimental realization of spin squeezing in a dense ensemble of NV centers, demonstrating a clear path toward overcoming classical limits in solid-state platforms. To further formalize and scale these phenomena, this work develops theoretical frameworks for generating robust spin squeezing under realistic experimental conditions. We show that finite-temperature easy-plane magnetism can be actively leveraged to create scalable squeezed states for the dipolar spin systems on regular lattices. Building upon this, we further extend the result to spatially disordered quantum dipoles. We demonstrate that strongly coupled spin pairs suppress squeezing through dynamical heating, and we propose a selective shelving protocol to mitigate this problem. Furthermore, we also propose a universal protocol for quantum-enhanced sensing that exploits information scrambling, utilizing the natural, scrambling dynamics of strongly interacting many-body systems to effectively amplify weak external signals. Together, the findings detailed in this thesis establish a foundational paradigm for controlling and utilizing solid-state spin ensembles, paving the way for entanglement-enhanced quantum sensors.
Point defects in diamond, particularly nitrogen-vacancy (NV) centers, have emerged as powerful tools for a broad range of quantum technologies. These defects are promising candidates for quantum information science, serving as deterministic single-photon sources and solid-state quantum memories. They have also been employed as nanoscale quantum sensors to detect various physical quantities, including magnetic fields, electric fields, and temperature, owing to their long spin coherence time at room temperature. Development of these diamond-based quantum technologies has been rapidly boosted by a recent quantum leap in nanofabrication technologies for high-quality single-crystal diamond. Incorporating these color centers into diamond nanostructures with mature integrated photonics provides a promising route to build scalable and practical systems for quantum applications. This review discusses recent progress and challenges in the hybrid integration of diamond color centers on cutting-edge photonic platforms. Nitrogen-vacancy centers in diamond have emerged as powerful tools for a broad range of quantum technologies. This review discusses recent progress and challenges in the hybrid integration of diamond color centers on cutting-edge photonic platforms.
Entanglement is central to quantum science and technology. Atomic defects in two-dimensional (2D) van der Waals (vdW) materials offer exciting prospects for quantum sensing, with spatial resolution reaching 1 nm demonstrated using scanning probe techniques. However, entangling qubits in vdW materials remains elusive. Here we report room-temperature quantum entanglement between an optically addressable electron spin and a strongly coupled 13^{13}13C nuclear spin in hexagonal boron nitride (hBN). We extend the electron spin coherence to 38 μμμs with dynamical decoupling, and create maximally entangled Bell states with a fidelity up to 0.89. We further use the nuclear spin as a long-lived quantum memory to enhance AC magnetic field sensing via correlation spectroscopy. These results establish entangled spin qubits in hBN as a robust platform for advanced quantum technologies based on 2D materials.