||NIST's "optics table on a chip" is a superconducting circuit on a square sapphire chip about 6 millimeters wide. Scientists use the chip to place a single microwave photon in two frequencies, or colors, at the same time. The photon is prepared by an "artificial atom" (small yellow square) in the middle of the chip. The arrow shape at the lower left connects to a transmission line used to tune the SQUID (small black area near the point of the arrow). The SQUID couples together two resonant frequencies of the cavity (meandering line), and the photon oscillates between different superpositions of those frequencies.