Quantum entangled radar theory and a correction method for the effects of the atmosphere on entanglement

A quantum entangled radar uses entangled photons instead of separate photons. It has been shown that for quantum entangled interferometers that the value of quantum entanglement deteriorates in an environment with attenuation. This paper introduces a correction method that allows the quantum radar to maintain excellent performance even when dealing with an environment with attenuation. The correction method is analogous to techniques used in adaptive optics to improve images. Correction approaches based on signal sources deliberately introduced into the environment and electromagnetic sources already present in the environment are considered. Closed form expressions for estimating the range error are derived for the cases when the radar uses N entangled photons for imaging or N separate imaging photons. Simulations of radar range error estimates for entangled and separate photon cases for propagation media with widely varying attenuation properties are provided. Comparisons of estimates with and without atmospheric correction are given. The atmospheric correction method extends the range of the beneficial effects of entanglement by a factor of 82, i.e. to 5000 km for a slowly varying propagation medium. For a propagation medium with 50 times as much variation, the atmospheric correction method offers super sensitivity for three times the range of the uncorrected case.