Tiny mechanical oscillators have enabled us to directly see quantum effects. They are limited, however, by the fact that they must be physically attached to something: this link to the environment can be a source of thermal noise that destroys the delicate quantum states. A scheme for separating a resonator from its surroundings by levitating it is now independently put forward by two teams of researchers (O.Romero-Isart et al. Phys. Rev. Lett. 109, 147205; 2012 and M.Cirio et al. Phys. Rev. Lett. 109, 147206; 2012).
Romero-Isart et al. theoretically investigated a superconducting micrometre-sized sphere, made of lead for example. The resonator considered by Cirio et al. comprised a nickel–zinc microsphere suspended above three orthogonal superconducting rings. Both teams placed a loop of superconducting wire known as a flux qubit near their resonator: the magnetic flux passing through the qubit depends strongly on the position of the resonator. The researchers were able to show how this resonator–qubit magnetic coupling could be used to cool the motion of the resonator to near the quantum ground state.
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