Quantum theory notoriously sets limits on how precisely we can make measurements. But the quirks of the quantum realm can also be turned to advantage. Physicists have now demonstrated a way to almost double measurement precision when using photons to gauge distances.
Like markings on a ruler, the orderly waves of laser light can be used to measure lengths. In an interferometer, a laser beam is split into two beams that take two different paths. The beams bounce off mirrors and converge at the other end of