Extended Data Fig. 3: A detailed schematic diagram of the experimental setup.

The 780 nm probe and reference beams generated from a calcite beam displacer are propagating in parallel through a room-temperature Rb vapor cell, with the probe beam overlapping with a counterpropagating coupling beam. Their transmission signals are detected on a balanced photon detector (PD) for differential measurement. The output intensity of the 780 nm laser from the fiber (monitored by an independent PD) is controlled by an AOM, whose RF driving is modulated by a waveform generator. QWPs are used to control the polarization of the lasers illuminating the atoms.