Synopsis: Atom Interferometers at Full Tilt

An atom interferometer serves as a sensitive tiltmeter that can measure Earth’s tidal deformations.
Synopsis figure
W.-J. Xu et al., Phys. Rev. A (2017)

Atom interferometers allow sensitive measurements based on interference effects between atoms so cold that they behave as waves. They have been used, for instance, to measure the fine-structure constant and to build rotation sensors. Experiments have now demonstrated that atom interferometers can act as ultrasensitive tiltmeters—devices that measure the tilt of a surface relative to the vertical direction, as determined by the force of gravity. The scheme achieves a sensitivity sufficient to observe Earth’s deformations due to tides.

The device designed by Zhong-Kun Hu and colleagues at the Huazhong University of Science and Technology, China, is based on an established atom-interferometry configuration that is applied, for the first time, to measuring tilt. First, a cloud of a million ultracold rubidium atoms is launched upward along a parabolic trajectory. Shortly after the launch, pulses from two counterpropagating lasers split the cloud into two atomic wave packets—one made of atoms in their ground state and the other of atoms excited by the lasers. Then, near the end of the atoms’ journey, more pulses from the same beams recombine the two groups of atoms. From the fringes resulting from quantum interference between the two wave packets, the researchers derive the angle between the laser beams and the force of gravity, which is the tilt.

The team showed that the sensitivity of the device was nearly 1000 times better than that of the best previously reported tiltmeter based on atomic interferometry. In experiments conducted continuously over 1.5 days in an underground lab, the researchers demonstrated the potential for geophysical uses by observing the tide-induced daily tilt of Earth’s surface.

This research is published in Physical Review A.

–Matteo Rini

Matteo Rini is the Deputy Editor of Physics.


Features

More Features »

Announcements

More Announcements »

Subject Areas

Atomic and Molecular Physics

Previous Synopsis

Next Synopsis

Related Articles

Synopsis: Imaging Water Molecules on Metal
Nanophysics

Synopsis: Imaging Water Molecules on Metal

Atomic force microscopy reveals the structure of a single layer of water molecules adsorbed on a nickel surface, potentially expanding our understanding of catalysis.   Read More »

Focus: Cooling on the Negative Side
Atomic and Molecular Physics

Focus: Cooling on the Negative Side

A new cooling technique targets negative ions, which are typically resistant to cooling methods that work with atoms and positive ions. Read More »

Synopsis: A Heat Engine Made of a Single Ion Spin
Quantum Physics

Synopsis: A Heat Engine Made of a Single Ion Spin

By converting electron spin into ion motion, researchers build a simple heat engine out of a single calcium ion. Read More »

More Articles