Harvesting quantum coherence from axion dark matter

Quantum coherence is one of the most striking features quantum mechanics rooted in superposition principle. Recently it has been demonstrated that possible to harvest from a coherent scalar field. In order explore new method detecting axion dark matter, we consider point-like Unruh-DeWitt detector coupled field and quantify measure detector. We show can matter. To be more precise, two-level electron system an atom as this case, obtain $C=2.2\times 10^{-6}\gamma\, \left(T/1{\rm s}\right)$ where $T$ $\gamma$ are observation time Lorentz factor. At same time, mass $m_a$ probe determined by energy gap