Axionic Quantum Memory

We propose to store quantum information in the form of a dark-state axionic polariton. The axion is a leading dark matter candidate which couples linearly to light in the presence of a background electromagnetic field. In symmetry-protected topological phases of matter, such as topological insulators and Weyl semi-metals, axion-like modes arise when the symmetry that protects the phase spontaneously breaks down and an axion insulator phase is realized. By coherently controlling the background electromagnetic field, single photons can be converted into and retrieved from amplitude (phase) fluctuations of the spin (charge) density wave in topological insulators (Weyl semi-metals). We study the feasibility of the proposal in the context of recent progress realizing and characterizing axion insulator phases in rare-earth doped topological insulators and quasi-one dimensional Weyl semi-metals.