Rydberg Atomic RF Sensor-based Quantum Radar

Rydberg atom-based RF sensors offer distinct advantages over conventional dipole antennas for electric field detection. This paper presents a system model and performance analysis of a Rydberg atom-based quantum radar, which employs optical readout via lasers and photon detectors instead of circuit-based receivers. We derive the signal-to-noise ratio (SNR), compare it with classical radar, and estimate Doppler frequency using an invariant function-based method. Simulations show that the quantum radar achieves higher SNR and lower RMSE in velocity estimation than conventional radar.

💡 Research Summary

This paper proposes and analyzes a novel quantum radar architecture that replaces the conventional dipole antenna receiver with a Rydberg‑atom‑based radio‑frequency (RF) sensor while retaining a standard microwave transmitter. The authors first describe the physical principle of the Rydberg sensor: alkali atoms (cesium) confined in a centimeter‑scale vapor cell are driven by a weak probe laser (|1⟩↔|2⟩ transition) and a strong coupling laser (|2⟩↔|3⟩ transition) forming a ladder‑type four‑level system. An incident RF field couples the Rydberg states |3⟩↔|4⟩, producing a Rabi frequency Ω_RF proportional to the electric field amplitude. The atomic susceptibility χ(t) depends on the density‑matrix element ρ_21, whose imaginary part modulates the probe‑laser transmission.

In the radar scenario, the transmitted microwave signal E₁(t)=A₁cos(2πf₁t) illuminates a target; the reflected echo E₂(t)=A₂cos