Radio-Cooled Macroscopic Object.

Lasers have long been used to cool atoms in traps. By using light slightly mistuned with the atom’s own internal quantum energy levels, the light can progressively slow the atoms almost to a halt. The same principles can be applied to larger objects made of trillions of atoms, such as a thin silicon cantilever.

Although light cooling of a cantilever-specifically the cantilever’s oscillatory motions---has been achieved before, scientists at the NIST lab in Boulder, Colorado are the first to do this using radio-frequency circuitry. In the NIST experiment, a micron-sized cantilever is chilled from room temperature down to 45 K in a process called capacitive cooling, in which the cantilever, pelted with radio waves, slows down (vibrates less) by transferring energy to the surrounding radio frequency resonant circuit. One of the NIST scientists, Kenton Brown (krbrown@boulder.nist.gov, 303-497-4364) says that the potential advantage here is that the cooling of the cantilever can be accomplished with standard radio-frequency technology instead of with precision optical elements or lasers, making it easier to put the whole setup on a chip and to immerse the chip in a cryogenic environment.

Why chill the cantilever (think of a tiny up-and-down vibrating diving board) in the first place? Because a cold enough cantilever could demonstrate quantum behavior in a macroscopic object. Besides the fundamental interest in such a feat, it might pave the way to very sensitive detectors. (Brown et al., Physical Review Letters, upcoming article)