Atominterferometre

Atominterferometre is a device that exploits the wave nature of atoms to perform interferometry of matter waves. By splitting and recombining atomic wave packets with light pulses, it measures phase differences that arise from accelerations, rotations, or gravitational fields with high sensitivity. In a typical setup, sequences of laser pulses act as beam splitters and mirrors for the atoms, creating two coherent paths that are later recombined to produce interference.

The most common implementation is a Mach-Zehnder type light-pulse interferometer, using stimulated Raman transitions or Bragg diffraction to transfer momentum between internal states or momentum modes. Cold atoms are prepared in a magneto-optical trap, then launched in a vacuum chamber as an atomic fountain or held in optical or magnetic traps for interrogation. The resulting interference signal is read out from the atomic populations, which depend on a phase shift accumulated along the paths.

Quantitatively, the phase shift for linear acceleration is approximately φ ≈ k_eff a T^2, where k_eff is the effective wavevector of the light and T is the interrogation time. Rotations produce a Sagnac-type phase shift, enabling sensitive measurements of angular motion. Applications include gravimetry and gradiometry for geophysics, inertial sensing for navigation, and tests of fundamental physics such as equivalence principle investigations or measurements of fundamental constants. There are ongoing efforts to deploy atom interferometers in field settings, on aircraft or ships, and in space for advanced metrology and future gravitational-wave detection.

Key challenges include environmental vibration, laser phase noise, magnetic fields, and the need for ultra-high vacuum and long interrogation times. Advances in laser cooling, shielding, and vibration isolation continue to improve performance.