Magneto-optical microscopies, including optical measurements of magnetic circular dichroism, are increasingly ubiquitous tools for probing spin-orbit coupling, charge-carrier g-factors, and chiral excitations in matter, but the minimum detectable signal in classical magnetic circular dichroism measurements is fundamentally limited by the shot-noise limit of the optical readout field. Here, we use a two-mode squeezed light source to improve the minimum detectable signal in magnetic circular dichroism measurements by 3 dB compared with state-of-the-art classical measurements, even with relatively lossy samples like terbium gallium garnet. We also identify additional opportunities for improvement in quantum-enhanced magneto-optical microscopies, and we demonstrate the importance of these approaches for environmentally sensitive materials and for low temperature measurements where increased optical power can introduce unacceptable thermal perturbations.
@article{arxiv.2305.02904,
title = {Quantum Enhanced Probes of Magnetic Circular Dichroism},
author = {Chengyun Hua and Claire E. Marvinney and Seongjin Hong and Matthew Feldman and Yun-Yi Pai and Michael Chilcote and Joshua Rabinowitz and Raphael C. Pooser and Alberto Marino and Benjamin J. Lawrie},
journal= {arXiv preprint arXiv:2305.02904},
year = {2023}
}