Synopsis: Freezing a 2D Ion Crystal

A laser scheme cools more than a hundred vibrational modes of a 2D crystal to close to their quantum mechanical ground state.
Synopsis figure
E. Jordan/NIST

For decades, researchers have attempted to cool macroscopic mechanical oscillators down to their quantum mechanical ground state. So far, however, they have only cooled a few selected vibrational modes of such oscillators. Now, Elena Jordan of the National Institute of Standards and Technology in Boulder, Colorado, and coworkers have simultaneously cooled all the “drumhead” modes of a thin 2D crystal made of 150 trapped beryllium (Be +) ions. The cooling of these modes—which resemble the out-of-plane vibrational modes of a drum’s membrane—could allow use of large trapped-ion crystals in applications including metrology and quantum simulation.

The researchers created a 2D lattice of trapped Be+ions using magnetic and electric fields. To cool the lattice vibrations, the team used a laser-cooling scheme that exploits quantum interference effects between the atoms’ multiple energy levels to reduce the ions’ kinetic energies. Researchers previously used a version of this technique to simultaneously reduce the energy of multiple motional degrees of freedom, cooling the vibrational modes of a linear string of 18 atoms. Jordan and her coworkers now show that the scheme can cool mesoscopic systems with hundreds of atoms. They simultaneously froze all 150 drumhead vibrational modes of the Be+ion array.

In their experiments, the researchers only cooled drumhead modes—in-plane vibrations, for example, remained untouched. However, they say that freezing out drumhead modes is particularly beneficial for quantum simulation applications involving ion crystals. For instance, having lower-amplitude drumhead modes could allow ion crystals to more faithfully simulate the Ising model, which describes a system of interacting spins on a lattice.

This research is published in Physical Review Letters.

—Matteo Rini

Matteo Rini is the Deputy Editor of Physics.


Features

More Features »

Announcements

More Announcements »

Subject Areas

Atomic and Molecular Physics

Previous Synopsis

Computational Physics

Extra Dimensions Give Optimization a Boost

Read More »

Next Synopsis

Particles and Fields

Neutrino Probes of Long-Range Interactions

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 »

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