Quantum gravity gradiometer makes first find outside lab

Birmingham University researchers from the UK National Quantum Technology Hub in Sensors and Timing have reported their achievement in Nature.

The quantum gravity gradiometer, developed under contract for the Ministry of Defence and in the UKRI-funded Gravity Pioneer project, was used to find a tunnel buried outdoors one metre below the ground surface.

In use, the quantum gravity sensor measures subtle changes in the pulling strength of gravitational fields when a cloud of atoms is dropped.

Professor Kai Bongs, head of Cold Atom Physics at Birmingham University and Principal Investigator of the UK Quantum Technology Hub Sensors and Timing, explained that atoms are put into a quantum superposition of traveling along two different trajectories simultaneously and the respective matter wave phases are allowed to interfere at the end.

This gives rise to a phase-depended imbalance between the number of atoms in one quantum state and the number of atoms in another quantum state.