Figure 4
(a) Plot of the cooperativity of the readout beam as a function of damped mechanical linewidth. (b) Plot of the measured ratios
(blue ○) and
(pink ○). (c) Plot of the mechanical mode phonon occupancy,
, as a function of the optically damped mechanical linewidth,
. The dashed line is the predicted phonon number
from an ideal backaction cooling model. Vertical error bars in (b) and (c) indicate uncertainty in the calibrated phonon occupancy due to uncertainty in the system parameters and a 95% confidence interval on the Lorentzian fits to spectra. (d) Plot of the asymmetry (
) in the measured Stokes and anti-Stokes sidebands of the readout laser for each calibrated measurement of
. The horizontal error bars arise from a 2% uncertainty in the transmitted readout laser beam power between detunings
, and a 95% confidence interval in the Lorentzian fits to the measured spectra. The vertical error bars in
are the same as in (c). The classical (blue curve) and quantum mechanical (pink curve) relations for the sideband asymmetry are also plotted. (e)–(g) Plot of the measured Stokes (red curve) and anti-Stokes (blue curve) readout beam spectra for (from top to bottom)
, 6.3, and 3.2 phonons. For clarity, we have divided out the readout backaction from each spectra by multiplying the measured spectra at detunings
by
. Additionally, we have plotted the horizontal axis in units of
, and rescaled the vertical axis for different
to keep the areas directly comparable. The difference in the Stokes and anti-Stokes spectra, which arises due to the quantum zero-point fluctuation of the mechanical system, is shown as a shaded region.
Reuse & Permissions