Synopsis: Spinning a Condensate with Light

A spiral pattern of light imparts angular momentum to a quantum condensate in a semiconductor.
Synopsis figure
R. Dall et al., Phys. Rev. Lett. (2014)

The collective quantum state called a Bose-Einstein condensate was first created using ultracold atoms, and it has recently been demonstrated using composite particles in specialized semiconductor structures. These semiconductor-based versions form at higher temperatures and could potentially be used for sensitive detectors or novel optoelectronic devices, but they are harder to manipulate directly. Now an international team led by Elena Ostrovskaya of the Australian National University in Canberra has shown how a patterned light source can modify the internal state of the condensate, specifically by giving it a net rotation.

To form a condensate, researchers employ semiconductor microcavities that confine both light and light-generated electron-hole pairs to form combined “exciton-polaritons.” If the light is bright enough to create a high density of these quasiparticles, they can spontaneously form a condensate, even at temperatures approaching room temperature. But the detailed wave information in the light is lost in making the pairs, and thus cannot be used to tailor the condensate’s properties as is done in atomic systems.

The new experiments exploited the natural motion of newly generated pairs toward bright regions where other pairs have already condensed. By patterning the illumination in an asymmetrical spiral pattern, the researchers used this quasiparticle flow to impart angular momentum to the entire condensate, which they confirmed by measuring the phase variation of the luminescence it emitted. Among other applications, the circulating condensate might be useful for devices reminiscent of existing SQUID detectors, which use circulating electric currents in superconductors to measure tiny magnetic fields.

This research is published in Physical Review Letters.

–Don Monroe


More Features »


More Announcements »

Subject Areas

Atomic and Molecular PhysicsQuantum Physics

Previous Synopsis

Quantum Information

Simon Says Speed Up

Read More »

Next Synopsis


Unraveling the Vortex

Read More »

Related Articles

Synopsis: Putting the Squeeze on Magnetic Resonance

Synopsis: Putting the Squeeze on Magnetic Resonance

Electron-spin-resonance measurements can achieve greater sensitivity using squeezed light as an input. Read More »

Synopsis: Direct View of Exchange Symmetry
Quantum Physics

Synopsis: Direct View of Exchange Symmetry

A proposed set of experiments could offer a direct measurement of the fundamental quantum property that distinguishes fermions from bosons. Read More »

Synopsis: Topological Defect on the Move
Condensed Matter Physics

Synopsis: Topological Defect on the Move

Researchers have directed the motion of a domain-wall-like topological defect through a crystal of trapped ions. Read More »

More Articles