- According to quantum mechanics, a mechanical resonator cooled to its ground state will continue to exhibit fluctuations in position. This so-called zero-point motion, a type of quantum noise, previously demonstrated for trapped ions, has now been directly measured for a chip-scale nanomechanical resonator cooled near its quantum ground state. In a paper to be published in PRL physicists, use a fabricated silicon nanomechanical resonator coupled to laser light, to both cool, and read-out the motion of mechanical system. This method of cooling, called electromagnetic back-action cooling, has been of interest for some time, as an effective means to remove all thermal noise from a mechanical resonator. Such cooling methods have only recently been successful at achieving this task, but only using read-out techniques ill-suited for observing the remaining quantum noise of motion. Using two lasers, one for back-action cooling, and the other for a two-shot read-out scheme, physicists have now measured the quantum motion of a nanomechanical system. By carefully measuring the rates at which the mechanical system can emit, and absorb energy from its surround environment, the authors demonstrate an asymmetry with no classical analogue, and provide a self-calibrated method of thermometry of the nanomechanical resonator.
