Measuring low-frequency electric fields with high precision is still a major scientific challenge. Existing sensing technologies often fall short when trying to achieve three key goals at once: accurate calibration, compact size, and the ability to determine both the strength and direction of a field. Rydberg atoms have emerged as a promising solution in the field of quantum metrology. These atoms are extremely sensitive to electric fields because of their large electric dipole moments, and their behavior can be tied to well-known atomic properties. This makes them attractive for building highly accurate sensors. Most current methods for detecting low-frequency or DC electric fields with Rydberg atoms rely on vapor-cell electromagnetically induced transparency (EIT) spectroscopy. However, this technique has important drawbacks. Because it uses a gas of atoms, effects such as Doppler broadening, collisional broadening, and averaging across many atoms can blur the signal.…