The Axion Soliton Correlometry Interferometer (ASCI): A Kilometer-Baseline Search for Macroscopic Quantum Coherence in Dark Matter

Abstract

We propose a novel experimental concept to directly probe the spatial coherence of the galactic axion dark matter field. Motivated by persistent anomalies in haloscope coherence measurements and robust theoretical predictions of gravitationallybound solitons (axion stars) in ultra-light scalar fields, we argue that a phasecorrelated network of detectors separated by O(10) km could detect the transit of such macroscopic quantum objects. This paper (1) reviews the theoretical coherence scale of the Standard Halo Model and hints of longer coherence in existing data, (2) details the predicted properties of dilute axion stars, (3) outlines the generic geometric signature of a soliton transit on a detector pair, (4) presents the conceptual design of the Axion Soliton Correlometry Interferometer (ASCI), and (5) defines a collaborative pathfinder program to develop this new observational axis in dark matter science. A detection would constitute proof of macroscopic quantum coherence in dark matter, while null results would constrain the abundance of solitonic structures in the galactic halo.