Determining the Phases of Radio Frequency Fields Using Interferometric Loops

A method, comprising:

• receiving a radio frequency (RF) signal at a vapor cell that contains a vapor, the vapor defining:
• an RF transition driven by the RF signal,
• a set of loop optical transitions that, together with the RF transition, form a closed loop of transitions, the set of loop optical transitions comprising a first loop optical transition, and
• a probe optical transition that shares an energy level with the first loop optical transition;
• receiving laser signals at the vapor cell to produce an output optical signal, the laser signals generated by a laser system and comprising:
• loop laser signals that drive the set of loop optical transitions, the loop laser signals comprising a detuned loop laser signal that drives, and is detuned relative to, the first loop optical transition, and
• a probe laser signal that drives the probe optical transition and produces the output optical signal;
• generating, by operation of an optical detector system, a detector signal in response to receiving the output optical signal at the optical detector system;
• and
• determining, by operation of a signal processing system, one or more properties of the RF signal based on the detector signal, the signal processing system in communication with the optical detector system.