Synopsis: Time doesn’t stand still

Researchers predict that modifying the design of atomic clocks could make them ten times more accurate than the current standard.
Synopsis figure
Credit: Courtesy A. Clairon/SYRTE

Time (or frequency) is the most precisely measured physical quantity by far. But finding ways to measure it even better could allow more powerful tests of fundamental physics, such as searches for changes in the fine-structure constant.

The world’s best time pieces are based on “atomic fountains,” in which lasers cool a cloud of alkali-metal atoms and then toss them gently upward. As the atoms fly up and then fall back down under the force of gravity, they pass twice along the axis of a cylindrical cavity filled with microwaves. By measuring how many atoms respond to the microwave field as they change the microwave frequency, researchers can adjust that frequency to within a few parts in 1016 of the value that defines the standard for a second.

Writing in Physical Review Letters, Jocelyne Guéna, of Systèmes de Référence Temps-Espace (SYRTE) at the Observatory of Paris, and her colleagues analyzed the imperfections that cause the largest, but nonetheless tiny, uncertainty in frequency. Using the clock at SYRTE, they verified experimentally how spatial variations in the microwave phase contribute to the error. The biggest contributions come from variations with a dipole or quadrupole dependence on angle in the horizontal plane. The collaboration between SYRTE and Pennsylvania State University predicts that independently feeding in the microwaves at four positions around the cylindrical cavity, instead of the current two, will reduce the clock errors from Doppler shifts to an unprecedented part in 1017. – Don Monroe


Features

More Features »

Announcements

More Announcements »

Subject Areas

Atomic and Molecular Physics

Previous Synopsis

Astrophysics

Tuning in to gravity

Read More »

Next Synopsis

Quantum Information

Preventive circuitry

Read More »

Related Articles

Synopsis: Quantum Sensing of Magnetic Fields
Quantum Physics

Synopsis: Quantum Sensing of Magnetic Fields

A new design for an atomic magnetometer utilizes so-called quantum nondemolition measurements to detect very weak magnetic-field signals. Read More »

Focus: New View of Cold Atoms Flowing
Atomic and Molecular Physics

Focus: New View of Cold Atoms Flowing

A new technique produces an image of the flow of cold atoms through a channel, a potentially important tool for future cold-atom technology. Read More »

Viewpoint: Seeing Scrambled Spins
Atomic and Molecular Physics

Viewpoint: Seeing Scrambled Spins

Two experimental groups have taken a step towards observing the “scrambling” of information that occurs as a many-body quantum system thermalizes.   Read More »

More Articles