Quantum Enhanced Probes of Magnetic Circular Dichroism

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, a two-mode squeezed light source is used to improve the minimum detectable signal in magnetic circular dichroism measurements by 3 decibels compared with state-of-the-art classical measurements, even with relatively lossy samples like terbium gallium garnet. These results provide a framework for new quantum-enhanced magneto-optical microscopies that are particularly critical for environmentally sensitive materials and for low temperature measurements where increased optical power can introduce unacceptable thermal perturbations. A two-mode squeezed light source generated through four-wave mixing in an atomic vapor was used to suppress the noise in magnetic circular dichroism measurements below the photon shot noise limit. This approach serves as a foundation for new quantum-enhanced probes of magneto-optical properties in materials that are sensitive to photothermally induced changes to basic material properties.image

Automated summary

In this study, a two-mode squeezed light source was used to improve the minimum detectable signal in magnetic circular dichroism measurements. Even in lossy samples, significant improvements were achieved. This approach provides a new quantum-enhanced probe for the magneto-optical properties of sensitive materials.