Ten-Second Electron-Spin Coherence in Isotopically Engineered Diamond

TL;DR

This study demonstrates record-long electron-spin coherence times and coherent optical transitions in isotopically engineered diamond with nitrogen-vacancy centers, advancing quantum network applications.

Contribution

It reports the first combination of long spin coherence and narrow optical linewidths in engineered diamond, enabling improved quantum information processing.

Findings

Electron-spin coherence time of 6.8 ms with Hahn echo.

Dynamical decoupling extends coherence to 11.2 seconds.

Optical linewidth near 17 MHz with spectral diffusion characterization.

Abstract

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 $^{13}\mathrm{C}$ 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 $T_2 = 6.8(1)$ ms for a Hahn echo and of $T_2^{DD} = 11.2(8)$ 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.