0 20 40 60 80 100
−0.15
−0.1
−0.05
0
0.05
0.1
0.15
0.2
Time[ms]
RF response [A.U.]
X
Y
R
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
0
500
1000
1500
2000
2500
f−fLar [kHz]
RF response [A.U.]
Experiment
Fit
ab
52 S1/2
52 P1/2
52 P3/2
F=1
F=2
F’=1
F’=2
F’=1
F’=2
F’=0
F’=3
Repump
Pump
Probe
-∆
Extended Data Fig. 1 | Magneto-optical resonance signal. a, Spin response to
an RF pulse. X and Y are the outputs of the lock-in amplifier, with a π/2 phase
difference between them. RX=+^22 Y is the demodulated amplitude. b, The
associated Fourier transformation of the spin response signal. fLar is the centre
frequency for demodulation, with the subscript ‘Lar’ representing ‘Larmor
frequency’. f is the actual frequency of the signal before demodulation.
f − fLar represents the frequency of the signal after demodulation, that is, at the
lock-in amplifier output. Inset, energy levels of^87 Rb. All the atoms are pumped
into the F = 2 , mF = −2 state, so that they are oriented along x. The magnetic field
leads to a splitting of the magnetic sublevels by the Larmor frequency ΩL. A.U.,
arbitrary units.