Precise control over massive mechanical objects is highly desirable for testing fundamental physics and for sensing applications. A very promising approach is cavity optomechanics, where a mechanical oscillator is coupled to a cavity. Usually, such mechanical oscillators are in highly excited thermal states and require cooling to the mechanical ground state for quantum applications, which is often accomplished by utilising optomechanical backaction. However, this is not possible for increasingly massive oscillators, as due to their low frequencies conventional cooling methods are less effective. Here, we demonstrate a novel cooling scheme by using an intrinsically nonlinear cavity together with a low frequency mechanical oscillator. We demonstrate outperforming an identical, but linear, system by more than one order of magnitude. While currently limited by flux noise, theory predicts that with this approach the fundamental cooling limit of a linear system can not only be reached, but also outperformed. These results open a new avenue for efficient optomechanical cooling by exploiting a nonlinear cavity.

Additional funding received by the Canada First Research Excellence Fund and by the Deutsche Forschungsgemeinschaft through the Emmy Noether program (Grant No. ME 4863/1-1) and the projects CRC 910 and CRC 183.