Synopsis: Atoms for Magnetism

A magnetometer based on laser measurements of atomic energy levels can detect a magnetic field one hundred billion times smaller than the Earth’s.
Synopsis figure
Courtesy J. Shi/Princeton University

Sensitive magnetic detectors are essential for applications ranging from land mine clearance to imaging the magnetic activity of our brains, as well as for fundamental investigations of the symmetry of nature’s laws. Superconductor-based magnetometers have been the primary devices for ultrasensitive detection for a number of years. But atomic magnetometers—based on gases of atoms like rubidium—have recently started to offer comparable or better sensitivity, with the advantage of not requiring bulky and expensive cryogenic cooling. Yet the most sensitive schemes could only work in a highly shielded environment, screened from the Earth’s own magnetic field. Now, writing in Physical Review Letters, Dong Sheng at Princeton University, New Jersey, and co-workers report an atomic magnetometer that can detect fields one hundred billion times smaller than the Earth’s while operating in a finite field.

Atomic magnetometers detect how internal atomic levels are split into different spin states through the Zeeman effect induced by the external magnetic field. Typically, a pump laser is used to “polarize” the atoms by populating specific spin states, and a probe laser reads out the spin precession, yielding a signal that is proportional to the magnetic field. Sheng et al. have introduced two key improvements. First, they used a multipass cell in which the probe laser beam passes many times through the rubidium vapor, enhancing the measured signal. Second, they used a fast time-resolved setup, allowing the measurement to take place within 1 millisecond of laser pumping, before mechanisms that cause spin relaxation—the ultimate limit to noise in these systems—kick in. The demonstrated sensitivity, on par with the best available sensors, can be achieved without the need to operate under a close-to-zero magnetic field. – Matteo Rini


Features

More Features »

Announcements

More Announcements »

Subject Areas

Atomic and Molecular PhysicsMagnetism

Previous Synopsis

Quantum Physics

Quantum-ness Put on the Scale

Read More »

Next Synopsis

Related Articles

Synopsis: A Sextet of Entangled Laser Modes
Atomic and Molecular Physics

Synopsis: A Sextet of Entangled Laser Modes

Researchers have entangled six modes of a laser cavity—a record number for such a device. Read More »

Focus: Comprehensive Measurement of an Ion Beam
Atomic and Molecular Physics

Focus: Comprehensive Measurement of an Ion Beam

A new technique provides the first measurement of all six characteristics of a particle beam, which will help researchers improve beam quality. Read More »

Synopsis: Observing the Birth of a Nanoplasma
Atomic and Molecular Physics

Synopsis: Observing the Birth of a Nanoplasma

A femtosecond-sensitive technique reveals the first steps in the creation of the nanoplasma that forms when a powerful x-ray pulse hits a nanoparticle. Read More »

More Articles