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arXiv:2606.04497

Arbitrary manipulation of nuclear spins in hexagonal boron nitride

Fattah Sakuldee, Mehdi Abdi

quant-phcond-mat.otherSubmitted Jun 3, 2026• Announced Jun 4, 2026
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Abstract

Due to its localized nature and controllability, the negatively charged boron vacancy centers (V$_\text{B}^-$) in hexagonal boron nitride (hBN) are a promising spin platform for accessing its neighboring nuclei with potential for performing quantum computational tasks. However, the methods of utilizing and manipulating the nuclear spins are still lacking. In this work, we propose a protocol for the preparation of single- and multi-qubit gates on the nuclear spins, utilizing the electron spin as an auxiliary qubit. By applying a background magnetic field and a multi-tone continuous drive, we show that the electron spin coupling to the nuclei can be efficiently engineered. This allows for suppressing the undesired electron-nuclear interactions through the Hahn echo pulse sequence. The target gates are then implemented by employing proper RF drives. Our numerical results for realistic parameters show gate fidelities as high as $99\%$ for single-qubit and $95\%$ for multi-qubit gates. With the gate execution durations being less than $300$ ns, our protocol evades electron spin decoherence effects. Therefore, our scheme sets the stage for the practical application of V$_\text{B}^-$ in hBN for quantum computation purposes.

Related papers

Synchronous manipulation of nuclear spins via boron-vacancy centers in hexagonal boron nitride

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We develop a method for entangling operations on nuclear spins surrounding a negatively charged boron-vacancy (V B -center) point defect in hexagonal boron nitride (h BN ). To this end, we propose to employ the electron spin of a V B center as a control qubit. We show that, in the presence of a background magnetic field and by applying control pulses, one can collectively manipulate the state of the nuclei with U ^ z and U ^ x rotations. These rotations can serve for implementing the synchronous three-qubit X , Z , and Hadamard gates. Through our numerical analyses considering realistic system parameters and decoherence effects, we demonstrate that these gates can be executed with high fidelities. Furthermore, as an example for the application of our toolbox, we use these collective gates to prepare the highly entangled Greenberger-Horne-Zeilinger states among the three nuclear spins with a fidelity of 0.99. By including electron decoherence effects, we find that the relative deviations of the gate fidelities from the noisy terms are negligibly small, demonstrating the noise resilience of our protocols. Our work can serve as the foundation for exploiting the nuclear spins in h BN in future quantum technological applications.

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Stabilizing entanglement of boron-vacancy defects in a hexagonal boron-nitride membrane by two-phonon driving

Yi‐Fan Qiao, Xue‐Feng Pan, Xiao-Yu Yao +2 more

Generating stable entanglement by mimicking a squeezed environment plays an important role in quantum metrology and quantum information. Here, we propose an efficient scheme for generating stable entanglement of two boron-vacancy (VB) defects in a suspended circular hexagonal boron nitride ($h$-BN) membrane via a two-phonon drive. Compared to other reported methods, our scheme only needs a linear resource and thus is more convenient for experimental implementation. In the presence of a gradient magnetic field, the electronic spin degree of freedom of the VB defect can be coupled to the mechanical mode of $h$-BN membrane through spin-phonon interaction. The coupling strength is closely related to the geometry of the magnetic field and the parameters of the membrane, which allows us to realize different coupling regimes by choosing the parameter appropriately. After applying a time-dependent pump to the $h$-BN membrane, we can modulate its spring constant and obtain a tunable two-phonon drive to the mechanical mode. We then investigate the dissipative coupling between two VB spins in the condition of a large dissipation limit, showing that the stable entanglement can be generated under a two-phonon drive. In addition, we also take the spin dephasing into consideration to explore the robustness of our scheme. We then extend this scheme to multiparticle systems, which shows that the entanglement degree deepens with the increase of VB spin number. This work offers a fascinating platform for generating stable entanglement with VB spins in two-dimensional $h$-BN.

Physical Review A•Feb 18, 2025•1 citation
Due to its localized nature and controllability, the negatively charged boron vacancy centers (VB−_\text{B}^-B−​) in hexagonal boron nitride (hBN) are a promising spin platform for accessing its neighboring nuclei with potential for performing quantum computational tasks. However, the methods of utilizing and manipulating the nuclear spins are still lacking. In this work, we propose a protocol for the preparation of single- and multi-qubit gates on the nuclear spins, utilizing the electron spin as an auxiliary qubit. By applying a background magnetic field and a multi-tone continuous drive, we show that the electron spin coupling to the nuclei can be efficiently engineered. This allows for suppressing the undesired electron-nuclear interactions through the Hahn echo pulse sequence. The target gates are then implemented by employing proper RF drives. Our numerical results for realistic parameters show gate fidelities as high as 99%99\%99% for single-qubit and 95%95\%95% for multi-qubit gates. With the gate execution durations being less than 300300300 ns, our protocol evades electron spin decoherence effects. Therefore, our scheme sets the stage for the practical application of VB−_\text{B}^-B−​ in hBN for quantum computation purposes.
We develop a method for entangling operations on nuclear spins surrounding a negatively charged boron-vacancy (V B -center) point defect in hexagonal boron nitride (h BN ). To this end, we propose to employ the electron spin of a V B center as a control qubit. We show that, in the presence of a background magnetic field and by applying control pulses, one can collectively manipulate the state of the nuclei with U ^ z and U ^ x rotations. These rotations can serve for implementing the synchronous three-qubit X , Z , and Hadamard gates. Through our numerical analyses considering realistic system parameters and decoherence effects, we demonstrate that these gates can be executed with high fidelities. Furthermore, as an example for the application of our toolbox, we use these collective gates to prepare the highly entangled Greenberger-Horne-Zeilinger states among the three nuclear spins with a fidelity of 0.99. By including electron decoherence effects, we find that the relative deviations of the gate fidelities from the noisy terms are negligibly small, demonstrating the noise resilience of our protocols. Our work can serve as the foundation for exploiting the nuclear spins in h BN in future quantum technological applications.
Carbon-related defects in hexagonal boron nitride are promising room-temperature single-spin qubits and quantum sensors, but their atomic structures remain largely unidentified. Here we show, using first-principles calculations of electron-spin decoherence, that the atomic structure of each defect is imprinted in its spin coherence. Mapping the Hahn-echo dynamics of seven candidate carbon defects across magnetic field and four isotope-engineered nuclear-spin baths, we find that electron-spin-echo envelope modulation emerges at defect-specific magnetic fields, at which the nearest-neighbor nuclear spins satisfy a cancellation condition set by their hyperfine and quadrupole couplings. Both the fields and the modulation frequencies follow from an analytical model using computed hyperfine and quadrupole tensors alone, and they shift or vanish upon isotope substitution. At low fields, the field dependence of the coherence time separates the defects into two classes according to the sublattice occupied by carbon. These decoherence fingerprints, directly testable in isotope-engineered samples, establish a structural identification route complementary to optical spectroscopy.
The negatively charged boron vacancy ($\VB$) in hexagonal boron nitride (\hBN{}) was the first optically addressable spin qubit identified inside a van der Waals crystal, allowing atomically defined placement relative to a target. Its coherence in bulk \hBN{} is limited by the boron nuclei of the layers flanking the defect plane, which a thin flake removes. Here, we use a generalized cluster-correlation expansion with an extended central-spin block to calculate the Hahn-echo coherence time of $\VB$ in h11^{11}11B15^{15}15N as a function of layer number. Our results show that T2T_2T2​ rises from $199\ns$ in the bulk limit to $653\ns$ in a monolayer, a factor of 3.33.33.3 that is already saturated at three layers and that a sublattice decomposition attributes entirely to boron. The enhancement is confined to low field, is insensitive to stacking registry and twist angle, and requires alignment to within about two degrees, an onset we reproduce with no free parameters. Under dynamical decoupling, a 1/e1/e1/e threshold returns $206\ns$ for every thickness, but this is a zero of the first-shell modulation rather than a decay: measured without a threshold, the layer contrast survives and reaches a factor of 170170170. Layer number thus emerges as a design parameter for $\VB$-based sensing.
Hybrid quantum registers, such as electron-nuclear spin systems, have emerged as promising hardware for implementing quantum information and computing protocols in scalable systems. Nevertheless, the coherent control of such systems still faces challenges. Particularly, the lower gyromagnetic ratios of the nuclear spins cause them to respond slowly to control fields, resulting in gate times that are generally longer than the coherence time of the electron. Here, we demonstrate a scheme for circumventing this problem by indirect control: we apply a small number of short pulses only to the electron and let the full system undergo free evolution under the hyperfine coupling between the pulses. Using this scheme, we realize robust quantum gates in an electron-nuclear spin system, including a Hadamard gate on the nuclear spin and a controlled-NOT gate with the nuclear spin as the target qubit. The durations of these gates are shorter than the electron coherence time, and thus additional operations to extend the system coherence time are not needed. Our demonstration serves as a proof of concept for achieving efficient coherent control of electron-nuclear spin systems, such as nitrogen vacancy centers in diamond. Our scheme is still applicable when the nuclear spins are only weakly coupled to the electron.
Color centers that enable nuclear-spin control without RF fields offer a powerful route towards simplified and scalable quantum devices. Such capabilities are especially valuable for quantum sensing and computing platforms that already find applications in biology, materials science, and geophysics. A key challenge is the coherent manipulation of nearby nuclear spins, which serve as quantum memories and auxiliary qubits but conventionally require additional high-power RF fields which increase the experimental complexity and overall power consumption. Finding systems where both electron and nuclear spins can be controlled using a single MW source is therefore highly desirable. Here, using a modified divacancy center in silicon carbide, we show that coherent control of a coupled nuclear spin is possible without any RF fields. Instead, MW pulses driving the electron spin also manipulate the nuclear spin through hyperfineenhanced effects, activated by a precisely tilted external magnetic field. We demonstrate high-fidelity nuclear-spin control, achieving 89% two-qubit tomography fidelity and nearly T1-limited nuclear coherence times. This approach offers a simplified and scalable route for future quantum applications.
Generating stable entanglement by mimicking a squeezed environment plays an important role in quantum metrology and quantum information. Here, we propose an efficient scheme for generating stable entanglement of two boron-vacancy (VB) defects in a suspended circular hexagonal boron nitride (hhh-BN) membrane via a two-phonon drive. Compared to other reported methods, our scheme only needs a linear resource and thus is more convenient for experimental implementation. In the presence of a gradient magnetic field, the electronic spin degree of freedom of the VB defect can be coupled to the mechanical mode of hhh-BN membrane through spin-phonon interaction. The coupling strength is closely related to the geometry of the magnetic field and the parameters of the membrane, which allows us to realize different coupling regimes by choosing the parameter appropriately. After applying a time-dependent pump to the hhh-BN membrane, we can modulate its spring constant and obtain a tunable two-phonon drive to the mechanical mode. We then investigate the dissipative coupling between two VB spins in the condition of a large dissipation limit, showing that the stable entanglement can be generated under a two-phonon drive. In addition, we also take the spin dephasing into consideration to explore the robustness of our scheme. We then extend this scheme to multiparticle systems, which shows that the entanglement degree deepens with the increase of VB spin number. This work offers a fascinating platform for generating stable entanglement with VB spins in two-dimensional hhh-BN.