A type of interferometer that makes use of quantized energy levels in atoms. It consists of a beam of atoms and two pairs of lasers that are perpendicular to the atomic beam, with the second pair of lasers being in the direction opposite to the first pair. The interference pattern produced by this type of interferometer enables fundamental constants to be measured accurately. The Ramsey–Bordé interferometer is named after Norman Ramsey (1915–2011) and Christian Bordé (1943– ). Ramsey devised it in 1949, with Bordé developing it further in the 1980s.