Fig. 2: Thermal performance and quantum cross-correlations.
From: Low-noise optomechanical single phonon-photon conversion for quantum networks
a The blue dots show the thermal phonon occupancy nth of the mechanical mode as a function of intracavity photon number (bottom) and anti-Stokes scattering probability (top). Error bars originate from errors in the calibration of the detection path efficiency (see Supplementary Information). The orange dots indicate the signal-to-noise (SNR) ratio in the conversion process. b Cross-correlation function \({g}_{{{{\rm{S,aS}}}}}^{(2)}\) between optomechanically scattered photons from the write and read pulse as a function of anti-Stokes scattering probability of the readout pulse. The insert shows the pulse sequence used for the cross-correlation measurement. A blue-detuned write pulse creates a single phonon, which is read out by a red-detuned read pulse after a delay time of Tdelay = 150 ns. The pulse sequence is repeated with a repetition period of Trep = 10 μs. The Stokes scattering probability of the write pulse is fixed at pS = 1.3%. The blue shaded area corresponds to the theoretically expected dependence \({g}_{{{{\rm{S,aS}}}}}^{(2)}=1+{e}^{-{T}_{{{{\rm{delay}}}}}/{\tau }_{{{{\rm{m}}}}}}/({p}_{{{{\rm{s}}}}}+{n}_{{{{\rm{th}}}}})\) (see Supplementary Information), where nth is calibrated from the results in a and τm = 1.0 μs is the phonon lifetime of the mechanical mode (see Supplementary Information). The dashed horizontal line and shaded area underneath indicate the regime of classical correlations \({g}_{{{{\rm{S,aS}}}}}^{(2)}\le 2\). The error bars are calculated from the photon counting statistics and correspond to the 68% confidence interval of the binomial distribution.
