Quantum electromagnetic scattering and the sidelobe advantage

Quantum remote sensing, also known as Quantum Detection and Ranging (QUDAR), is the use of entangled photon states to detect targets at a stand-off distance. It inherently relies on sending many single photons through free space, bouncing off of a target and returning to the sensor. It is therefore necessary to understand how single photons interact and scatter from targets of macroscopic size. This paper relates quantum and classical scattering in the far field regime. Specifically, we show that due to the photon's position uncertainty, the path over which the photon traverses is not well defined, and this causes quantum interference. The result of this interference exactly replicates classical scattering behavior of electromagnetic waves. We will show that one can exactly derive the classical electric field scattering integral using a purely quantum construction. Although this paper focuses on the context of QUDAR, it is very general to any application involving far-field electromagnetic scattering.