Quantum leap for phonon lasers

Quantum leap for phonon lasers: "Light and sound are similar in various ways: they both can be thought of in terms of waves, and they both come in quantum mechanical units (photons in the case of light, and phonons in the case of sound). In addition, both light and sound can be produced as random collections of quanta (consider the light emitted by a light bulb) or orderly waves that travel in coordinated fashion (as is the case for laser light). Many physicists believed that the parallels imply that lasers should be as feasible with sound as they are with light. "