Physicists at the National Institute of Standards and Technology (NIST) have demonstrated entanglement—a phenomenon peculiar to the atomic-scale quantum world—in a mechanical system similar to those in the macroscopic everyday world. The work extends the boundaries of the arena where quantum behavior can be observed and shows how laboratory technology might be scaled up to build a functional quantum computer.
The research, described in the June 4 issue of Nature,* involves a bizarre intertwining between two pairs of vibrating ions (charged atoms) such that the pairs vibrate in unison, even when separated in space. Each pair of ions behaves like two balls connected by a spring (see figure), vibrating back and forth in opposite directions. Familiar objects that vibrate this way include pendulums and violin strings.
The NIST achievement provides insights into where and how "classical" objects may exhibit unusual quantum behavior. The demonstration also showcased techniques that will help scale up trapped-ion technology to potentially build ultra-powerful computers relying on the rules of quantum physics. If they can be built, quantum computers may be able to solve certain problems, such as code breaking, exponentially faster than today’s computers.