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arXiv:2411.07196 · Physical Review Letters

Lifetime-Limited and Tunable Emission from Single Charge-Stabilized Nickel Vacancy Centers in Diamond

I. M. Morris, T. Lühmann, Kai Klink, Logan Crooks, David Hardeman, Daniel J. Twitchen, Sébastien Pezzagna, Jan Meijer, Shannon S. Nicley, Jonas N. Becker

Published Jul 1, 2025• 5 citations
arXivHTMLPDF

Abstract

The negatively charged nickel vacancy center (NiV^{-}) in diamond is a promising spin qubit candidate with predicted inversion symmetry, large ground state spin-orbit splitting to limit phonon-induced decoherence, and emission in the near infrared. Here, we experimentally confirm the proposed geometric and electronic structure of the NiV defect via magneto-optical spectroscopy. We characterize the optical properties and find a Debye-Waller factor of 0.62. Additionally, we engineer charge state stabilized defects using electrical bias in planar all-diamond p-i-p junctions. We measure a vanishing static dipole moment and no spectral diffusion, characteristic of inversion symmetry. Under bias, we observe stable transitions with lifetime-limited linewidths as narrow as 16 MHz and convenient frequency tuning of the emission via a second-order Stark shift. Overall, this Letter provides a pathway toward coherent control of the NiV^{-} and its use as a spin qubit and contributes to a more general understanding of charge dynamics experienced by defects in diamond.

DOI
10.1103/wzjx-z2h5

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•Nov 19, 2018•2 citations
The negatively charged nickel vacancy center (NiV^{-}) in diamond is a promising spin qubit candidate with predicted inversion symmetry, large ground state spin-orbit splitting to limit phonon-induced decoherence, and emission in the near infrared. Here, we experimentally confirm the proposed geometric and electronic structure of the NiV defect via magneto-optical spectroscopy. We characterize the optical properties and find a Debye-Waller factor of 0.62. Additionally, we engineer charge state stabilized defects using electrical bias in planar all-diamond p-i-p junctions. We measure a vanishing static dipole moment and no spectral diffusion, characteristic of inversion symmetry. Under bias, we observe stable transitions with lifetime-limited linewidths as narrow as 16 MHz and convenient frequency tuning of the emission via a second-order Stark shift. Overall, this Letter provides a pathway toward coherent control of the NiV^{-} and its use as a spin qubit and contributes to a more general understanding of charge dynamics experienced by defects in diamond.
Quantum networks require qubits that combine efficient optical access, coherent control, and long-lived quantum memory, but realizing all three in one scalable platform remains a central bottleneck. Diamond color centers are leading candidates, yet widely studied defects retain tradeoffs among these capabilities. Here, we show that transition-metal defects in diamond provide a distinct route beyond these platforms by combining spin-orbit protected ground-state coherence, all-optical control, and near-infrared emission. Using a single nickel-vacancy (NiV−^-−), we demonstrate an all-optically controlled diamond spin qubit with coherence exceeding one millisecond at 1.65 K, compatible with compact closed-cycle cryogenics. We implement Raman Rabi oscillations and Ramsey interferometry and use all-optical dynamical decoupling to extend coherence from T2∗T_2^*T2∗​ = 371 ns to T2CPMG−4T_2^{CPMG-4}T2CPMG−4​ = 1.27 ms, establishing NiV−^-− as a deployable diamond spin-photon interface.
Solid-state quantum emitters that couple coherent optical transitions to long-lived spin qubits are essential for quantum networks. Here we report on the spin and optical properties of individual tin-vacancy (SnV) centers in diamond nanostructures. Through cryogenic magneto-optical and spin spectroscopy, we verify the inversion-symmetric electronic structure of the SnV, identify spin-conserving and spin-flipping transitions, characterize transition linewidths, measure electron spin lifetimes, and evaluate the spin dephasing time. We find that the optical transitions are consistent with the radiative lifetime limit even in nanofabricated structures. The spin lifetime is phonon limited with an exponential temperature scaling leading to T_{1}>10 ms, and the coherence time, T_{2}^{*} reaches the nuclear spin-bath limit upon cooling to 2.9 K. These spin properties exceed those of other inversion-symmetric color centers for which similar values require millikelvin temperatures. With a combination of coherent optical transitions and long spin coherence without dilution refrigeration, the SnV is a promising candidate for feasable and scalable quantum networking applications.
High Resolution Image Download MS PowerPoint Slide The negatively charged silicon vacancy center (SiV – ) in diamond is a promising, yet underexplored candidate for single-spin quantum sensing at sub-kelvin temperatures and tesla-range magnetic fields. A key ingredient for such applications is the ability to perform all-optical, coherent addressing of the electronic spin of near-surface SiV – centers. We present a robust and scalable approach for creating individual, ∼50 nm deep SiV – with lifetime-limited optical linewidths in diamond nanopillars through an easy-to-realize and persistent optical charge-stabilization scheme. The latter is based on single, prolonged 445 nm laser illumination that enables continuous photoluminescence excitation spectroscopy without the need for any further charge stabilization or repumping. Our results constitute a key step toward the use of near-surface, optically coherent SiV – for sensing under extreme conditions, and offer a powerful approach for stabilizing the charge-environment of diamond color centers for quantum technology applications.
Solid-state spin defects are a promising platform for quantum networks. A key requirement is to combine long ground-state spin-coherence times with a coherent optical transition for spin-photon entanglement. Here, we investigate the spin and optical coherence of single nitrogen-vacancy (NV) centres in (111)-grown isotopically engineered diamond. Our diamond-growth process yields a precisely controlled 13C^{13}\mathrm{C}13C concentration and low-ppb nitrogen concentrations. Combined with the mitigation of 50 Hz noise using a real-time feedforward scheme and tailored decoupling sequences, this enables record defect-electron-spin coherence times of T2=6.8(1)T_2 = 6.8(1)T2​=6.8(1) ms for a Hahn echo and of T2DD=11.2(8)T_2^{DD} = 11.2(8)T2DD​=11.2(8) s under dynamical decoupling. In addition, we observe coherent optical transitions with a near-lifetime-limited homogeneous linewidth of 16.9(4) MHz and characterize the spectral diffusion dynamics. These results provide new avenues to investigate the incorporation of impurities in diamond and new opportunities for improved spin-qubit control for quantum networks and other quantum technologies.
Color centers in diamond have attracted much interest as candidates for optically active, solid-state quantum bits. Of particular interest are inversion-symmetric color centers based on group-IV impurities in diamond because they emit strongly into their zero-phonon lines and are insensitive to electric field noise to first order. Early studies of the negatively charged tin-vacancy (${\mathrm{SnV}}^{\ensuremath{-}}$) center in diamond have found the ${\mathrm{SnV}}^{\ensuremath{-}}$ to be a promising candidate: it has high quantum efficiency, emits strongly into its zero-phonon lines, and is expected to have a long T2{T}_{2}T2​ spin coherence time at 4 K. To develop the ${\mathrm{SnV}}^{\ensuremath{-}}$ into a spin qubit requires further characterization, especially of the spin and optical properties of individual ${\mathrm{SnV}}^{\ensuremath{-}}$ in nanofabricated structures. In this work, we isolate single ${\mathrm{SnV}}^{\ensuremath{-}}$ centers in diamond nanopillars and characterize their emission properties and their spin response to a magnetic field. We observe narrow emission linewidths <250<250<250 MHz, as well as a strong polarization dependence of each transition. We also find the Zeeman splitting under a magnetic field to be in good agreement with theoretical prediction. Our results pave the way toward future employment of single ${\mathrm{SnV}}^{\ensuremath{-}}$ centers as optically accessible quantum memories.
Solid-state quantum emitters that couple coherent optical transitions to long-lived spin states are essential for quantum networks. Here we report on the spin and optical properties of single tin-vacancy (SnV) centers in diamond nanostructures. Through magneto-optical spectroscopy at 4 K, we verify the inversion-symmetric electronic structure of the SnV, identify spin-conserving and spin-flipping transitions, characterize transition linewidths, and measure electron spin lifetimes. We find that the optical transitions are consistent with the radiative lifetime limit and that the spin lifetimes are longer than for other inversion-symmetric color centers under similar conditions. These properties indicate that the SnV is a promising candidate for quantum optics and quantum networking applications.