The search for axion dark matter has achieved remarkable sensitivity through the development of high-Q resonators, quantum-limited amplifiers, and ultra-low-noise cryogenic technologies. However, most current experiments rely on direct power detection, where the weak physics signal itself must provide sufficient energy to be distinguished from the detector noise.

In this talk, I will present a coherent readout approach in which a strong reference field is introduced into the detector and the weak signal is measured through the modulation it induces on that reference. Through power detection, the signal mixes coherently with the reference field, producing an interference term that transfers information from an otherwise extremely weak signal onto a large carrier that can be measured with quantum-limited sensitivity. This approach is largely independent of the underlying detector architecture and can be applied to resonant, multimode, and broadband systems alike.

I will discuss the CARAMEL concept and its potential application to axion dark matter searches, emphasizing the possibility of employing a common quantum-limited readout strategy across a broad range of experimental approaches. The technique may be particularly attractive for future high-frequency searches, where detector complexity, multimode operation, and scalability become increasingly important.

The talk will also review recent progress achieved by the IBS Center for Axion and Precision Physics Research (CAPP), including quantum-limited searches in the 1–8 GHz range and the development of superconducting cavity technologies operating in strong magnetic fields. Building on these advances, I will discuss a possible path toward next-generation axion searches extending to substantially higher frequencies, where coherent readout techniques may offer new opportunities for improving sensitivity and discovery potential.