Origin of the microwave power-dependent resonance shift

Identify the origin of the microwave power-dependent shift in the silicon-vacancy center’s electron-spin resonance frequencies observed during microwave driving.

Background

The silicon-vacancy memory’s electron spin is driven by microwave pulses during the XY8 dynamical-decoupling sequence used for ion–memory entanglement. The authors observe that the electron-spin resonance frequency shifts as the microwave power changes; for a driving field with Rabi frequency 2π×282\pi\times28 MHz, they measure a detuning of +3.2+3.2 MHz.

Although the experiment accounts for this shift to maximize pulse fidelity, its physical origin is not resolved. Understanding the mechanism would clarify the microwave control behavior of the silicon-vacancy center and could improve calibration and coherent-control performance.

References

We note that we observe a MW power-dependent shift of the electron spin resonance frequencies that we must account for in order to achieve maximum pulse fidelity. For a driving field with Rabi frequency $2\pi\times28$\,MHz, we measure a detuning of +3.2\,MHz. We leave the origin of this shift for future work.

— Quantum Networking at the Speed of Quantum Computation: Kilohertz Entanglement in a Heterogeneous Quantum System  (2610.10705 - Hartung et al., 7 Oct 2026) in Supplemental Material, Section “Diamond nanophotonic SiV memory,” subsection “Microwave driving and nuclear spin initialization” (Section \ref{sec:SI:siv_mw})