Quantum-enhanced passive remote sensing

We investigate theoretically the ultimate resolution that can be achieved with passive remote sensing in the microwave regime used, e.g., on board of satellites observing Earth, such as the soil moisture and ocean salinity (SMOS) mission. We give a fully quantum mechanical analysis of the problem, starting from thermal distributions of microscopic currents on the surface to be imaged that lead to a mixture of coherent states of the electromagnetic field which are then measured with an array of antennas. We derive the optimal detection modes and measurement schemes that allow one to saturate the quantum Cram??r-Rao bound for the chosen parameters that determine the distribution of the microscopic currents. For parameters comparable to those of SMOS, a quantum enhancement of the spatial resolution by more than a factor of 20 should be possible with a single measurement and a single detector, and a resolution down to the order of 1 m and less than a 110 K for the theoretically possible maximum number of measurements.

Automated summary

In this study, we theoretically investigate the ultimate resolution achievable with passive remote sensing in the microwave regime used for satellite observations of Earth, such as the SMOS mission. We provide a fully quantum mechanical analysis of the problem, considering thermal distributions of microscopic currents on the surface to be imaged and their coherent mixture with the electromagnetic field, which is then measured using an array of antennas. We derive the optimal detection modes and measurement schemes that can saturate the quantum Cram??r-Rao bound for the chosen parameters, and find that a quantum enhancement of spatial resolution by more than a factor of 20 should be possible in certain parameter regimes.