Quantum sensing in millikelvin regime

Recently, color centers with accessible spins have been demonstrated as a versatile quantum sensing platform to investigate microscopic electromagnetic behaviors in solid-state materials with unprecedented spatial resolution and field sensitivity. Despite the remarkable progress made thus far, pioneering and current quantum sensing research are mostly limited in the conventional ⁴He cryogenic temperatures and above, experimental demonstration of sub-Kelvin quantum sensing in real materials environment remains a formidable challenge in the current state-of-the-art. Here we report our recent efforts on developing dilution refrigerator-based multimodal quantum sensing microscopy to timely address this challenge. We show versatile millikelvin quantum sensing using different solid-state spin defect candidates. Our results pave the way for designing next-generation quantum metrology technologies, which may find a broad range of applications in the forefront of materials science, condensed matter physics, and quantum revolution research.