As a direct result of the quantum nature of electromagnetic radiation, all forms of light exhibit inherent and unavoidable random fluctuations. Because these fluctuations reveal information about the nature of light and the underlying processes that generate it, they have received considerable attention since the time of Einstein. But they are also a source of noise that limits the accuracy with which information can be transmitted by a beam of light. Although experiments often still struggle with instrumental noise, some are quickly approaching the measurement limits set by the quantum‐statistical nature of light. With the help of new techniques to “squeeze” the uncertainty of light, researchers can now conduct experiments with greater precision than possible with laser light. The generation of various forms of squeezed light in recent years has raised hopes for its application to such diverse areas as gravity‐wave detection based on optical interferometry and reduced‐error lightwave communications.
New techniques that exploit the limits of the uncertainty principle promise nearly noise‐free optical measurements and improved optical information transmission.