Figure 2: Examples of recent progress in optomechanical cooling. The initial and final phonon numbers are plotted vs mechanical frequency divided by the optical linewidth. The quantum limit for optomechanical cooling is indicated as a blue curve [29, 30]. $ωM/κ≪1$ is the “bad cavity” limit, and $ωM/κ≫1$ is the “good cavity” limit, for which Eq. (1) holds and ground-state cooling is possible. Red labels indicate cooling from room temperature, blue labels refer to cryogenic setups. Initial phonon numbers vary even for the same temperature due to different frequencies. Data (and setup pictures, left to right) from experiments at MIT [6], Laboratoire Kastler Brossel (LKB) [9], Yale [15], Vienna (IQOQI) [32], MPQ Munich [33], and JILA at Boulder [34].