New silicon device simplifies squeezing light to reduce quantum noise

Nature : All light is affected by noise from quantum effects. At the low powers used by the lasers in many sensors, light fluctuations caused by noise can blur the classical light waves and thus limit the precision of measurements made using the light. “Squeezing” the light can reduce the noise, but only in one dimension—any change to the height of a light wave’s peaks affects the distance between the peaks. Most light-squeezing work has focused on gravitational-wave detectors, where researchers have experimented with passing lasers through crystals. The researchers at the Laser Interferometer Gravitational-Wave Observatory (LIGO) have successfully squeezed light to achieve sensitivities better than the standard limit, but the process is difficult. Now, Oskar Painter of Caltech has developed a simple zipper-like device carved on a basic silicon chip that also squeezes light, albeit at higher frequencies than are useful for gravitational-wave detectors. When a laser passes between the two arms of the zipper, its photons bounce off the arms. The amount of noise in the light determines how hard the photons push against the arms. By changing the angle of the arms, the frequency of the light can be tuned. Because the prototype leaks light, it can only squeeze out 5% of the fluctuations from noise. Painter hopes to attain up to 90% by improving the zipper quality. Although other groups are also working on methods for squeezing light, Painter’s device may be the simplest so far.