Initial radio frequency Simulations of Sub-Wavelength Antenna structures for Solid-State Defects
Solid state defects are a promising candidate for many applications in quantum technologies [1-3], whereas their potential usage as qubits for quantum computing is most prominent. [3] Therefor, quantum state manipulation needs to be performed and necessitates resonant microwave excitation at specific frequencies (such as the nitrogen-vacancy center (NV) at 2,87GHz) [4]. While established antenna designs exist for defects like the NV, emerging quantum defects, such as the ASiSii-defect family, [5] require excitation at distinct frequencies, demanding tailored antenna structures.
This work introduces initial COMSOL Multiphysics® simulations using the RF-Module for the development of micro-antennas targeting frequencies around 1GHz. The structures aim to maximize the magnetic field amplitude in a small volume (≈1mm3) where the material containing defects will be located. Thereby antenna design faces significant challenges: operation under cryogenic temperatures (< 10K) and in high vacuum, severe miniaturization constraints, and most critically, physical dimensions significantly smaller than the operating wavelength. This sub-wavelength regime renders traditional analytical “textbook” antenna design approaches ineffective, making full-wave electromagnetic simulation the indispensable design tool.
The presented simulations represent the first step in modeling the near-field RF performance of candidate antenna geometries. Utilizing COMSOL’s capabilities allows us to assess critical performance parameters, such as the magnetic field intensity, its distribution and S-parameters. An efficient antenna structure forms the essential baseline for Rabi-driven spin manipulation of solid-state defects.
This preliminary simulation work establishes the foundational basis for future prototype fabrication and experimental validation. It underscores the necessity of electromagnetic simulation for advancing the microwave control hardware required for next-generation quantum defects in solid-state systems.
