Physicists propose a tabletop quantum sensor to detect Earth’s frame-dragging effect.

The Story

Earth’s rotation is already measurable on a tabletop; Earth’s spacetime twist still awaits a working laboratory instrument.

The proposal is a serious calculation built on known quantum-sensing methods, but it is still a proposal. Tabletop interferometry has measured Earth’s rotation, while frame dragging is far smaller and has so far been detected with satellites. The decisive test is whether the helium device, junction, membranes and noise control can achieve the predicted sensitivity in practice.

• What is establishedQuantum optical interferometry has measured Earth’s rotation, demonstrating that tabletop quantum sensors can resolve extremely small rotational signals.
• What remains openThe proposed helium-4 gyrometer has not yet demonstrated the full frame-dragging measurement, so its projected precision is not an experimental result.

• The Berkeley-led team proposes measuring frame dragging with a superfluid helium-4 Josephson-junction gyrometer and calculates very high sensitivity at millikelvin temperatures.journals +1
• A separate tabletop experiment measured Earth’s rotation with path-entangled photons in a 715-square-meter interferometer, showing the feasibility of sensitive quantum rotation measurements but not frame-dragging detection.arxiv
• A published analysis of quantum clock interferometry says frame-dragging effects appear too small for current technology in that proposed setup.arxiv