Sandia National Laboratories’ four-channel, silicon photonic single-sideband modulator chip, measuring 8 millimeters on each side and marked with a green Sandia thunderbird logo, sits inside packaging that incorporates optical fibers, wire bonds, and ceramic pins. Credit: Craig Fritz, Sandia National Laboratories ==================================================================== A milestone in quantum sensing is drawing closer, promising exquisitely accurate, GPS-free navigation. Peel apart a smartphone, fitness tracker or virtual reality headset, and inside you’ll find a tiny motion sensor tracking its position and movement. Bigger, more expensive versions of the same technology, about the size of a grapefruit and a thousand times more accurate, help navigate...