Wed. Jan 26th, 2022

Use of time extension to measure the curvature of space-time

FIG. S1. 52hp gradiometer model, Rx = 5.8 cm. Top left: deflection of upper arm (light blue), forearm (dark blue) and midpoint (black) of upper 52hp interferometer due to source mass as a function of time, scaled by -52k. Top right: deflection of upper arm (light blue), forearm (dark blue) and midpoint (black) of lower 52hp interferometer, scaled by -52k. Bottom left: time integral of source mass potential along the upper arm (pink) and forearm (dark red) on the upper 52hp interferometer. Bottom right: time integral of source mass potential along the upper arm (pink) and forearm (dark red) on the lower 52hp interferometer. Credit: DOI: 10.1126 / science.abl7152

A team of researchers working at Stanford University has used time expansion in an atomic fountain to measure the curvature of space-time. In their study, reported in the journal Science, the group used the fountain as an interferometer to measure atomic wave packet changes similar to phase shifts. Albert Roura, along with the German Aerospace Center’s Institute of Quantum Technologies, published a Perspective piece in the same journal issue outlining the team’s work in California.

The nuclear fountain created by the team consisted of a 10 meter high tower with a vacuum tube – on top there was a ring that secured a piece of tungsten. To use the fountain, they fired lasers under individual atoms, pushing them upward, and other lasers fired down from the top to stop them. A third laser pulse captured the atom as it reached the bottom. In their experiments, the scientists pushed pairs of atoms up the fountain and measured the resulting phase shifts as they traveled up and down the fountain. Phase shift was initiated by stopping the atoms at different distances from tungsten at the top of the fountain. The setup demonstrated phase shift due to time expansion, where time, as described in Einstein’s theory of relativity, moves more slowly closer to massive objects. In the fountain, the atoms that rose higher moved closer to the tungsten mass and therefore experienced more acceleration, which led to a time shift between them and the atoms that did not rise as high.

The experiments also showed that the Aharonov-Bohm effect also applies to gravity, as a magnetic field inside a cylindrical container can affect particles that never enter the container. In their atomic fountains, electrons taking unique paths up and down the fountain were forced into superpositions, and despite the magnetic field in the chamber, no magnetic force was exerted on them; yet there were still signs of magnetic field shifts.

Molecular fountains lead to more accurate measurement of physical constants

More information:
Chris Overstreet et al., Observation of a Gravitational Aharonov-Bohm Effect, Science (2022). DOI: 10.1126 / science.abl7152.

Albert Roura, quantum probe for space-time curvature, Science (2022). DOI: 10.1126 / science.abm6854.

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Citation: Using Time Extension to Measure the Curvature of Space-Time (2022, January 14) Retrieved January 14, 2022 from

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