Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2601.05013

Landau Zener Interaction Enhanced Quantum Sensing in Spin Defects of Hexagonal Boron Nitride

Mohammad Abdullah Sadi, Tiamike Dudley, Luca Basso, Thomas Poirier, James H. Edgar, Jacob Henshaw, Peter A. Bermel, Yong P. Chen, Andrew Mounce

quant-phSubmitted Jan 8, 2026• Announced Jan 9, 2026
arXivHTMLPDF

Abstract

Negatively charged boron vacancies (V$_{\text{B}}^{-}$) in hexagonal boron nitride (hBN) comprise a promising quantum sensing platform, optically addressable at room temperature and transferrable onto samples. However, broad hyperfine-split spin transitions of the ensemble pose challenges for quantum sensing with conventional resonant excitation due to limited spectral coverage. While isotopically enriched hBN using $^{10}$B and $^{15}$N isotopes (h$^{10}$B$^{15}$N) exhibits sharper spectral features, significant inhomogeneous broadening persists. We demonstrate that, implemented via frequency modulation on an FPGA, a frequency-ramped microwave pulse achieves around 4-fold greater $|0\rangle\rightarrow|-1\rangle$ spin-state population transfer and thus contrast than resonant microwave excitation and thus 16-fold shorter measurement time for spin relaxation based quantum sensing. Quantum dynamics simulations reveal that an effective two-state Landau-Zener model captures the complex relationship between population inversion and pulse length with relaxations incorporated. Our approach is robust and valuable for quantum relaxometry with spin defects in hBN in noisy environments.

Related papers

Multi-frequency composite pulse sequences for sensitivity enhancement in hexagonal boron nitride quantum sensor

Hao Gu, Yuki Nakamura, Kento Sasaki +1 more

Abstract A negatively charged boron vacancy ( V B − ) in hexagonal boron nitride (hBN) has recently started to be used as a magnetic sensor. However, V B − has magnetic resonance spectra broadened by hyperfine interactions, which decreases the signal contrast and thus degrades the magnetic field sensitivity. Here we propose multi-frequency composite pulse sequences to enhance the contrast of the measurement signal in the Rabi oscillation. We demonstrate that the sequence using five microwave frequencies enhances the signal contrast, improving the sensitivity by a factor of 2.3 compared to the conventional sequence.

Applied Physics Express•May 1, 2023•7 citations

Quantum Simulation and Nanoscale Sensing of Many-Body Phenomena with Solid-State Spin Defects

G. He

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 Cr$_{1+\delta}$Te$_2$/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.

•Jun 10, 2026•0 citations

Energy-Transfer-Enhanced Emission and Quantum Sensing of VB- Defects in hBN-PbI2 Heterostructures

Eveline Mayner, Yaroslav Zhumagulov, Cristian de Giorgio +6 more

Spin defects in two-dimensional materials hold significant potential for quantum information technologies and sensing applications. The negatively charged boron vacancy (VB-) in hexagonal boron nitride (hBN) has attracted considerable attention as a quantum sensor due to its demonstrated sensitivity to temperature, magnetic fields, and pressure.1 However, its applications have thus far been limited by inherently dim photoluminescence (PL). By fabricating a van der Waals heterostructure with a sensitizing donor layer, lead iodide (PbI2), we effectively enhance the PL intensity from the VB- by 5-45x, while maintaining compatibility with other heterostructures and vdW optoelectronic platforms. The type-I band alignment at the heterojunction enables efficient exciton migration while suppressing back-electron transfer, and the strong spectral overlap between the PbI2 emission and defect absorption supports efficient fluorescence resonance energy transfer. Ab initio density functional theory (DFT) predicts a photon-ratcheting mechanism that boosts absorption and emission while maintaining magnetic resonance (ODMR) contrast through minimal hybridization. Experimentally, the heterostructure exhibits enhanced continuous-wave ODMR sensitivity and functions as a precise probe of external magnetic fields. This work establishes a proof-of-concept for amplifying weak defect signals in nanomaterials, highlighting a new strategy for engineering their optical and magnetic responses.

cond-mat.mtrl-sciCross-listedarXiv:2602.02256•Feb 3, 2026

Acoustic-phonon-driven spin-lattice relaxation of the hBN boron vacancy in the sub-THz regime

Priyo Adhikary, Pramey Upadhyaya

The negatively charged boron vacancy center in hexagonal boron nitride is a premier candidate for quantum sensing, yet its performance is critically limited by longitudinal spin-lattice relaxation time ($T_1$). A microscopic understanding of spin relaxation in the high magnetic field regime remains elusive, as the relevant Zeeman transitions lie far below the optical phonon energies typically invoked to describe the relaxation process. Here, we apply an \textit{ab initio} acoustic mode spin-phonon relaxation theory to this problem and quantitatively reproduce the experimental magnetic field and temperature dependence of $T_1$ without empirical fitting parameters. We demonstrate that the relaxation dynamics are driven by a direct one-phonon emission and absorption process resonant with the Zeeman splitting. Furthermore, we identify the out-of-plane flexural phonon branch which is unique to two-dimensional hosts, as the primary source of decoherence, creating a distinct low-energy spectral function that facilitates spin relaxation. Our results provide a microscopic interpretation of the experimentally observed non-monotonic field and temperature dependence in two-dimensional quantum defect centers.

cond-mat.mtrl-sciCross-listedarXiv:2607.07642•Jul 9, 2026

Room-Temperature Electrical Readout of Spin Defects in van der Waals Materials

Shihao Ru, Liheng An, Haidong Liang +14 more

Negatively charged boron vacancy ($\mathrm{V_B^-}$) 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 $\mathrm{V_B^-}$ 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 $\mathrm{V_B^-}$ 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.

quant-pharXiv:2511.08874•Nov 13, 2025

Correlating spin and optical properties of quantum emitters in hBN

Nika Teran, Benjamin Whitefield, Nicholas Sloane +3 more

Optically addressable spin defects in hexagonal boron nitride (hBN) are well suited for near-surface quantum sensing. They offer bright, wavelength-tunable single-photon emission with high optically detected magnetic resonance (ODMR) contrast at room temperature. Here we controllably synthesise a high density of spin-complex defects in carbon-doped hBN flakes. We find that the zero-field splitting parameter D is directly correlated with the zero-phonon line of an emitter, while the ODMR contrast shows no such correlation. We further analyse an individual narrowband defect showing 68% ODMR contrast and enhance its photon collection by ~40% using a solid immersion lens. By advancing both the practical synthesis of the spin complexes and the understanding of their microscopic origin, our results move us toward the deterministic creation of ODMR-active quantum emitters

quant-pharXiv:2608.03090•Aug 5, 2026
Negatively charged boron vacancies (VB−_{\text{B}}^{-}B−​) in hexagonal boron nitride (hBN) comprise a promising quantum sensing platform, optically addressable at room temperature and transferrable onto samples. However, broad hyperfine-split spin transitions of the ensemble pose challenges for quantum sensing with conventional resonant excitation due to limited spectral coverage. While isotopically enriched hBN using 10^{10}10B and 15^{15}15N isotopes (h10^{10}10B15^{15}15N) exhibits sharper spectral features, significant inhomogeneous broadening persists. We demonstrate that, implemented via frequency modulation on an FPGA, a frequency-ramped microwave pulse achieves around 4-fold greater ∣0⟩→∣−1⟩|0\rangle\rightarrow|-1\rangle∣0⟩→∣−1⟩ spin-state population transfer and thus contrast than resonant microwave excitation and thus 16-fold shorter measurement time for spin relaxation based quantum sensing. Quantum dynamics simulations reveal that an effective two-state Landau-Zener model captures the complex relationship between population inversion and pulse length with relaxations incorporated. Our approach is robust and valuable for quantum relaxometry with spin defects in hBN in noisy environments.
Abstract A negatively charged boron vacancy ( V B − ) in hexagonal boron nitride (hBN) has recently started to be used as a magnetic sensor. However, V B − has magnetic resonance spectra broadened by hyperfine interactions, which decreases the signal contrast and thus degrades the magnetic field sensitivity. Here we propose multi-frequency composite pulse sequences to enhance the contrast of the measurement signal in the Rabi oscillation. We demonstrate that the sequence using five microwave frequencies enhances the signal contrast, improving the sensitivity by a factor of 2.3 compared to the conventional sequence.
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.
Spin defects in two-dimensional materials hold significant potential for quantum information technologies and sensing applications. The negatively charged boron vacancy (VB-) in hexagonal boron nitride (hBN) has attracted considerable attention as a quantum sensor due to its demonstrated sensitivity to temperature, magnetic fields, and pressure.1 However, its applications have thus far been limited by inherently dim photoluminescence (PL). By fabricating a van der Waals heterostructure with a sensitizing donor layer, lead iodide (PbI2), we effectively enhance the PL intensity from the VB- by 5-45x, while maintaining compatibility with other heterostructures and vdW optoelectronic platforms. The type-I band alignment at the heterojunction enables efficient exciton migration while suppressing back-electron transfer, and the strong spectral overlap between the PbI2 emission and defect absorption supports efficient fluorescence resonance energy transfer. Ab initio density functional theory (DFT) predicts a photon-ratcheting mechanism that boosts absorption and emission while maintaining magnetic resonance (ODMR) contrast through minimal hybridization. Experimentally, the heterostructure exhibits enhanced continuous-wave ODMR sensitivity and functions as a precise probe of external magnetic fields. This work establishes a proof-of-concept for amplifying weak defect signals in nanomaterials, highlighting a new strategy for engineering their optical and magnetic responses.
The negatively charged boron vacancy center in hexagonal boron nitride is a premier candidate for quantum sensing, yet its performance is critically limited by longitudinal spin-lattice relaxation time (T1T_1T1​). A microscopic understanding of spin relaxation in the high magnetic field regime remains elusive, as the relevant Zeeman transitions lie far below the optical phonon energies typically invoked to describe the relaxation process. Here, we apply an \textit{ab initio} acoustic mode spin-phonon relaxation theory to this problem and quantitatively reproduce the experimental magnetic field and temperature dependence of T1T_1T1​ without empirical fitting parameters. We demonstrate that the relaxation dynamics are driven by a direct one-phonon emission and absorption process resonant with the Zeeman splitting. Furthermore, we identify the out-of-plane flexural phonon branch which is unique to two-dimensional hosts, as the primary source of decoherence, creating a distinct low-energy spectral function that facilitates spin relaxation. Our results provide a microscopic interpretation of the experimentally observed non-monotonic field and temperature dependence in two-dimensional quantum defect centers.
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.
Optically addressable spin defects in hexagonal boron nitride (hBN) are well suited for near-surface quantum sensing. They offer bright, wavelength-tunable single-photon emission with high optically detected magnetic resonance (ODMR) contrast at room temperature. Here we controllably synthesise a high density of spin-complex defects in carbon-doped hBN flakes. We find that the zero-field splitting parameter D is directly correlated with the zero-phonon line of an emitter, while the ODMR contrast shows no such correlation. We further analyse an individual narrowband defect showing 68% ODMR contrast and enhance its photon collection by ~40% using a solid immersion lens. By advancing both the practical synthesis of the spin complexes and the understanding of their microscopic origin, our results move us toward the deterministic creation of ODMR-active quantum emitters