Quantum mechanics and its bizarre rules explain the structure of atoms, the formation of chemical bonds, and the switching of transistors in microchips. Oddly, though, in spite of the theory's name, physicists have never made an actual machine whose motion captures the quirkiness of quantum mechanics. Now a group from the National Institute of Standards and Technology (NIST) in Boulder, Colorado, has taken a step in that direction by forging a mind-bending quantum connection between two mechanical widgets. Their devices don't look like electric drills or other familiar machines, however: Each is a pair of ions oscillating in an electric field, like two marbles joined by a spring.
The link the researchers created is called entanglement, and it has been made before between certain internal properties of quantum particles, such as the inner gyrations of ions. The new work extends that link to the actual motion of the ions, which is a kind of micro-analog of the swinging of the pendulum of a grandfather clock. “For the first time, the mechanical motion itself has been entangled,” says Rainer Blatt, an experimental physicist at the University of Innsbruck in Austria.