Frequency-degenerate microwave quantum radar

Quantum radar technology offers a promising path to surpass classical radar systems by improving their signal-to-noise ratio (SNR) through the exploitation of quantum correlations and microwave single-photon detectors. Key elements of the quantum radar protocol include a source of quantum-entangled pair of signals and a joint nonlinear detector, for which theory predicts quantum advantage of up to 3 dB in terms of SNR. Here, we rely on superconducting parametric circuits to generate frequency-degenerate, two-mode squeezed states for object interrogation and joint detection within a nonlinear interferometer. We use a qubit-based microwave single-photon detector to sample one of the interferometer outputs and discriminate between different object hypotheses. We discuss the advantages of this approach and compare it to alternatives. Ultimately, this work shows simulations and early experimental results towards demonstrating quantum advantage in the chosen quantum radar setting, providing a perspective for microwave quantum sensing.