A millimeter-wave atomic receiver: sensitivity and selectivity

Rydberg quantum sensors are sensitive to radio-frequency fields across an ultra-wide frequency range spanning megahertz to terahertz electromagnetic waves resonant with Rydberg atom dipole transitions. The sensitivity in Rydberg quantum sensors at millimeter-wave frequencies is generally limited by a drop of the electric-dipole matrix elements (that scale as n^2) between low-lying Rydberg states and optical frequency and amplitude noise present in the quantum state readout. We demonstrate a millimeter-wave heterodyne atomic receiver using continuous-wave lasers locked to an optical frequency comb. We show first sensitivity measurements at a frequency of f = 95.992512 GHz (W-band) signal field and characterize the sensor selectivity to resonant millimeter-wave fields, obtaining signal rejection ratios for channel widths Delta f/f = 10^{-4}, 10^{-5} and 10^{-6}. Our work represents an important advance towards future studies and applications of atomic receiver science and technology and in weak millimeter-wave signal detection.