en.Wedoany.com Reported - A research team at Michigan State University has demonstrated a quantum bit based on nickel vacancy (NiV⁻) with a coherence time exceeding 1 millisecond under all-optical control.

This study positions transition metal defects as an alternative to nitrogen vacancy (NV) and silicon vacancy (SiV) color centers, combining long-lived quantum memory, optical control capabilities, and near-infrared photon emission characteristics. The findings have been published on the arXiv preprint platform.

Using all-optical dynamic decoupling techniques, the team extended the coherence time of a single NiV⁻ defect from 371 nanoseconds to 1.27 milliseconds. Through Raman Rabi oscillations and Ramsey interferometry, the qubit can be fully manipulated and read out via optical pulses. Unlike many quantum hardware platforms, the device operates at 1.65 Kelvin, compatible with compact closed-cycle cryostats without requiring dilution refrigerators.

Traditional diamond-based quantum hardware faces a long-standing challenge: combining efficient optical interfaces with sufficiently long coherence times to support practical quantum memories and networked quantum systems. The researchers indicate that the spin-orbit protected ground-state coherence and near-infrared photon emission properties of nickel vacancy defects make them potentially suitable for future distributed quantum computing and quantum network architectures.

The researchers also note that significant work remains before this platform can be deployed in large-scale systems. Current research involves a single nickel vacancy defect operating under cryogenic conditions. To approach the theoretically predicted coherence time of approximately 30 milliseconds, further improvements in material purity and isotopic engineering are required. Future work will focus on reliably creating and controlling multiple nickel vacancy defects, a necessary step toward scalable quantum devices and networked quantum systems.