Synopsis: Cold Atoms, Meet Flux Quanta

A cloud of atoms trapped close to a superconducting ring can detect the magnetic field inside the ring with single-quantum sensitivity.
Synopsis figure
P. Weiss et al., Phys. Rev. Lett. (2015)

Researchers are working on the development of hybrid quantum technologies that couple different quantum systems, such as cold atoms and superconducting circuits, to combine their respective strengths. Now Patrizia Weiß and colleagues at the University of Tübingen, in Germany, have used a cloud of ultracold atoms to detect discrete quanta of magnetic flux produced by a nearby superconducting ring. The researchers say that this result could lead to new kinds of quantum information devices, in which, for instance, a cold-atom cloud acts as a memory for the information processed by a superconducting circuit.

In the experiment, the team first applied a constant magnetic field while cooling down a 20-micrometer-wide niobium ring on a sapphire chip to a temperature below the superconducting transition. They then used additional magnetic fields to trap an ultracold rubidium cloud 18 micrometers below the ring. Since the ring’s magnetic field changed the shape (well depth) of the atom trap, it affected the number of trapped atoms. Finally, the team measured the laser absorption of the cloud to determine the number of atoms.

The magnetic flux threading a superconducting ring is always an integer multiple of the fundamental flux quantum, Planck’s constant divided by twice the electron charge (h/2e). Repeating the experiment with different magnetic field strengths, the authors found that the number of atoms changed with increasing field in discrete “jumps,” rather than continuously. The jump size matched predictions, suggesting that the jumps directly indicate the number of flux quanta in the ring.

This research is published in Physical Review Letters.

–David Ehrenstein


Features

More Features »

Announcements

More Announcements »

Subject Areas

Atomic and Molecular PhysicsQuantum Information

Previous Synopsis

Next Synopsis

Fluid Dynamics

Bubbles Pop, Droplets Don’t

Read More »

Related Articles

Viewpoint: A Quantum Defect Sees its Charged Surroundings
Magnetism

Viewpoint: A Quantum Defect Sees its Charged Surroundings

Nitrogen-vacancy centers in diamond are found to be more affected by local charge than expected, which has implications for the use of the defects as quantum sensors. Read More »

Synopsis: Ripples and Fireworks in Bose-Einstein Condensates
Atomic and Molecular Physics

Synopsis: Ripples and Fireworks in Bose-Einstein Condensates

By switching a magnetic field’s direction up and down, researchers interfered matter waves to produce density ripples that led to firework-like jets. Read More »

Focus: Twisted Light in a Photonic Chip
Optics

Focus: Twisted Light in a Photonic Chip

Light waves capable of storing quantum information can propagate through a photonic chip waveguide and potentially be used for on-chip computation. Read More »

More Articles