Mancini and colleagues' scheme makes use of the fact that when photons of light hit a mirror, they impart some momentum to it. The pressure of this radiation can make the mirror move. An intense light beam, such as a laser, bouncing back and forth between two movable mirrors can set up a standing wave that makes them oscillate.

The team calculates that entanglement should persist even at temperatures of four degrees above absolute zero - warm for the quantum world, and easy to achieve. Entangling macroscopic objects such as mirrors may provide a way to detect extremely weak forces with high precision, says Mancini2. Such weak forces have been proposed, for example, that modify Newton's law of gravity.