Synopsis: Less wiggle room for the gravitational constant

Ultracold atoms trapped in optical lattices allow high-precision measurement of the gravitational constant.
Synopsis figure
Credt: N. Poli et al., Phys. Rev. Lett. (2011)

Ultracold atoms have proven their value as test beds for creating new quantum states of matter and simulating how electrons behave in solids. Trapped and cooled atoms have also taken a starring role in high-precision measurements of fundamental constants and in atomic clocks. Writing in Physical Review Letters, Nicola Poli and colleagues at the University of Florence, Italy, report their use of ultracold strontium atoms to push forward our knowledge of Earth’s gravitational constant.

Building on prior proposals to use atoms captured in optical traps, Poli et al. transfer roughly one million strontium-88 atoms at 0.6μK into a vertically oriented optical lattice. Since the atoms move in a periodic potential, they undergo Bloch oscillations, similar to electrons in a solid-state lattice under the influence of an applied electric field. Bloch oscillations arise when the induced momentum change of the particle caused by a field interacts with the band structure of the lattice. In Poli et al.’s experiments, however, the applied field is gravity. By imaging the cloud of strontium atoms undergoing Bloch oscillations, the authors were able to measure the acceleration due to Earth’s gravitational field, g, to within 140ppb and compare the result with measurements by the best conventional gravimeter.

The authors say that their hope is that by optimizing the technique, measurements might become possible that test general relativity, theories of quantum gravity, and deviations from Newtonian gravity. – David Voss


Features

More Features »

Announcements

More Announcements »

Subject Areas

Atomic and Molecular PhysicsGravitation

Previous Synopsis

Biological Physics

Bubble trouble

Read More »

Next Synopsis

Spintronics

Two in one

Read More »

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 »

Synopsis: Hunting for Hair on Coalescing Black Holes
Gravitation

Synopsis: Hunting for Hair on Coalescing Black Holes

A fresh look at data from the first detected black-hole merger supports the “no hair” theorem and proves the potential of black-hole spectroscopy. 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 »

More Articles