Fig. 2: Squeezed light generation by collective spin modes.
From: Squeezed light from an oscillator measured at the rate of oscillation
a Homodyne signal PSDs at Δ/(2π) = 3 GHz and different detection angles ϕ indicated in the figure. The points are experimental data. The green and orange traces are obtained close to \({\hat{P}}_{{{{{{{{\rm{L}}}}}}}}}\) and \({\hat{X}}_{{{{{{{{\rm{L}}}}}}}}}\), respectively, and the olive, blue and purple—at intermediate quadratures. The gray trace shows the shot-noise level. The black curves are theoretical predictions based on the global fit over 15 quadratures (only 5 are shown, the rest are presented in the SI). The red curve is the optimum-quadrature squeezing spectrum predicted by the single-oscillator model. b The spectra of classically driven motion of the collective spin. The eight peaks visible at low probe powers correspond to bare oscillator modes due to the transitions between adjacent mF levels. Their frequencies are determined by the linear and quadratic Zeeman energies, and magnitudes are determined by the macroscopic populations of the mF levels as shown in the inset. The spectra at high powers expose the hybridized oscillator modes.
