# Synopsis: Laser Suppression of Noise

In laser metrology, adding additional laser pulses, separated in time from the first, suppresses energy line shifts and allows for even more precision.

Spectral purity makes the laser the tool of choice for precise analysis of the internal structure of atoms and molecules, but its intensity may shift the very energy levels under study, which limits metrology applications. In a paper in Physical Review Letters, Nils Huntemann at Physikalisch-Technische Bundesanstalt in Braunschweig, Germany, and colleagues report on a way to suppress these energy level shifts.

The authors build upon a precision spectroscopy technique developed by Norman Ramsey in the 1950s for nuclear magnetic resonance, which has become very important for atomic clocks and quantum information processing. In this scheme, one electromagnetic field prepares a quantum system, while a second spatially separated field interrogates the system after it evolves for a time. This method greatly reduces the perturbations of the energy states by the probing fields. Huntemann et al. replace the two separated fields with laser pulses separated in time, which, according to theory, eliminates the level shifts and reduces the sensitivity to laser intensity fluctuations. As a test case, they applied the method to a strongly forbidden electronic transition in a single trapped ytterbium-$171$ ion that would typically require high intensity to study, because of its low transition rate.

With this technique, which the authors call “hyper-Ramsey spectroscopy,” they were able to suppress the laser-induced line shift by four orders of magnitude. The hope is to eventually apply this approach to atomic clocks, time and frequency standards, and quantum information processing, where high stability and long coherence times are necessary. – David Voss

### Announcements

More Announcements »

Soft Matter

## Next Synopsis

Atomic and Molecular Physics

## Related Articles

Atomic and Molecular Physics

### Synopsis: Deep Freezing Molecules

Researchers cooled trapped molecules well below $1\phantom{\rule{2.22198pt}{0ex}}\text{mK}$—a record temperature for molecules that have not been assembled from pre-cooled atoms. Read More »

Atomic and Molecular Physics

### Viewpoint: Journey from Classical to Quantum in Two Dimensions

Two separate groups have extracted the thermodynamic equation of state for a two-dimensional gas of fermionic atoms, revealing its peculiar quantum features. Read More »

Quantum Physics

### Synopsis: Tiny Oscillator Works as Photon Changing Room

A new device converts the frequency of a photon using the vibrations in a mechanical oscillator. Read More »