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arXiv:2411.02828 · Physical Review Applied

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

Fattah Sakuldee, Mehdi Abdi

Published May 15, 2025• 1 citation
arXivHTMLPDF

Abstract

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.

DOI
10.1103/vlqs-h75g

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Selective control of qubits in a quantum register for the purposes of quantum information processing represents a critical challenge for dense spin ensembles in solid-state systems. Here we present a protocol that achieves a complete set of selective electron-nuclear gates and single nuclear rotations in such an ensemble in diamond facilitated by a nearby nitrogen-vacancy (NV) center. The protocol suppresses internuclear interactions as well as unwanted coupling between the NV center and other spins of the ensemble to achieve quantum gate fidelities well exceeding 99%. Notably, our method can be applied to weakly coupled, distant spins representing a scalable procedure that exploits the exceptional properties of nuclear spins in diamond as robust quantum memories.

arXiv:1602.06862•Physical Review Letters•Sep 20, 2016•47 citations
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.
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.
Motivated by the recent experimental progress in exploring the use of a nitrogen-vacancy (NV) center in diamond as a quantum computing platform, we propose schemes for fast and high-fidelity entangling gates on this platform. Using both analytical and numerical calculations, we demonstrate that synchronization effects between resonant and off-resonant transitions may be exploited such that spin-flip errors due to strong driving may be eliminated by adjusting the gate time or the driving field. This allows for fast, high-fidelity entangling operations between the electron spin and one or several nuclear spins. We investigate a two-qubit system where the NV center comprises a N 15 atom and a qubit-qutrit system for the case of a N 14 atom. In both cases, we predict a complete suppression of off-resonant driving errors for two-qubit gates when addressing the NV electron spin conditioned on states of nuclear spins of the nitrogen atom of the defect. Additionally, we predict fidelities > 0.99 for multiqubit gates when including the surrounding C 13 atoms in the diamond lattice in the conditioned logic.
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.
Abstract Color centers in solids, such as the nitrogen-vacancy center in diamond, offer well-protected and well-controlled localized electron spins that can be employed in various quantum technologies. Moreover, the long coherence time of the surrounding spinful nuclei can enable a robust quantum register controlled through the color center. We design pulse sequence protocols that drive the electron spin to generate robust entangling gates with these nuclear memory qubits. We find that compared to using Carr-Purcell-Meiboom-Gill (CPMG) alone, Uhrig decoupling sequence and hybrid protocols composed of CPMG and Uhrig sequences improve these entangling gates in terms of fidelity, spin control range, and spin selectivity. We provide analytical expressions for the sequence protocols and also show numerically the efficacy of our method on nitrogen-vacancy centers in diamond. Our results are broadly applicable to color centers weakly coupled to a small number of nuclear spin qubits.
Abstract The negatively charged boron vacancy center ( V B − ) in a hexagonal boron nitride ( h -BN) film, represents a promising quantum unit at room temperature due to its exceptional attributes, including remarkable sensitivity to magnetic field or strain, long coherence time, nearly perfect spin homogeneity, and an ultra-thin film structure. We here study a different hybridization proposal of an ensemble of V B − centres magnetically coupled to a superconducting flux qubit (FQ) or a DC superconducting quantum interference device (SQUID). Because the localization degree and density of the magnetic field in the FQ are much greater than that of the superconducting resonator (SR), this type of spins-FQ coupling is much stronger for an identical number of V B − centres, and it can therefore mimic the traditional light–matter interactions, i.e., the Dicke-, Tavis-Cummings- or Rabi-like model. For applications, this hybrid quantum system can potentially guarantee such as the simulation of quantum phase transitions (QPTs) of the anomalous Rabi-like model especially showing the influences to QPTs of the spins’ dephasing and FQ’s decay, criticality-enhanced quantum metrology or quantum sensing, the steady-state preparation of single- and two-mode spin-squeezed state (SSS). This investigation can potentially provide a platform for the subsequent quantum information processing (QIP).
Selective control of qubits in a quantum register for the purposes of quantum information processing represents a critical challenge for dense spin ensembles in solid-state systems. Here we present a protocol that achieves a complete set of selective electron-nuclear gates and single nuclear rotations in such an ensemble in diamond facilitated by a nearby nitrogen-vacancy (NV) center. The protocol suppresses internuclear interactions as well as unwanted coupling between the NV center and other spins of the ensemble to achieve quantum gate fidelities well exceeding 99%. Notably, our method can be applied to weakly coupled, distant spins representing a scalable procedure that exploits the exceptional properties of nuclear spins in diamond as robust quantum memories.