Novel atom interferometer may become an astronomical asset

Interferometry “signals” a new era in astronomy, enabling the direct observation of gravitational waves and allowing for signal targeting across a broad frequency spectrum. Traditional terrestrial gravitational wave detectors primarily relied on laser beams bouncing between reference mirrors along orthogonal baselines. However, many of these detectors are limited in sensitivity at lower frequencies due to fluctuations in Newtonian noise.

Scientists have proposed using atom interferometers, spaced along horizontal or vertical baselines, where a laser beam manipulates all interferometers to track baseline changes induced by gravitational waves.

This approach opens a new frequency band for gravitational wave observation, complementing current laser interferometers and the planned Laser Interferometer Space Antenna (LISA). However, they often face challenges with scalability and atomic expansion constraints.

Schubert et al. proposed another atom interferometry-based terrestrial detector for gravitational waves with frequencies between 0.3 Hz and 5 Hz.

“The novelty of our proposal in comparison to others is its geometry: how the atom interferometer is implemented by a specific choice of coherent atom-light interactions,” said author Christian Schubert. “It combines a multi-loop geometry with relaunches, such that only a single link is required for coherent manipulation of the pair of atom interferometers in a horizontal configuration.”

These “folded loop” interferometers for horizontal antennae promise several benefits. They reduce the requirements on the sources providing ultracold atoms for the interferometry – and the impact of error sources. They also combine the advantages of vertical detector geometries with those of horizontal baselines, especially scalability in length, which boosts detector sensitivity.

“the detector can operate in a broadband mode to find a signal and then be switched to a resonant mode, increasing the signal-to-noise ratio at a specific signal frequency,” said Schubert.

Source: “Scalable, symmetric atom interferometer for infrasound gravitational wave detection,” by C. Schubert, D. Schlippert, M. Gersemann, S. Abend, E. Giese, A. Roura, W. P. Schleich, W. Ertmer, and E. M. Rasel, AVS Quantum Science (2024). The article can be accessed at https://doi.org/10.1116/5.0228398 .