Trapping Atoms Better with Light

The atomic chamber in which atomic tractor beams were created. (Source: IPAS, Univ. Adelaide)

University of Adelaide researchers have delved into the realm of Star Wars and created a power­ful tractor beam or light-driven energy trap for atoms. Rather than sucking space-ships into a space-station, this tractor beam pulls atoms into a micro­scopic hole at the centre of a special optical fibre. It is opening the way for new quantum experi­ments that may lead to new secure communi­cations or advanced sensing tech­nologies. The researchers from the Uni­versity’s Institute for Photonics and Advanced Sensing (IPAS) say this is the first time that scientists have been able to demon­strate a highly efficient wave­guide trap.

The PhD student who developed the tech­nology, Ashby Hilton, says: “Although tractor beams are green or blue in the movies, in this case the trap is made of invi­sible infrared light. The beam grabs hold of atoms that are floating in a chamber that is almost completely emptied of gas. Every atom that enters the tractor beam is pulled into the fibre – there is no escape. And once sucked into the interior of the optical fibre the atoms can be held for long periods of time. Our experi­ments show that we can very precisely control light to produce exactly the right condi­tions to control atoms.”

The tractor beam works by the infrared light inter­acting with the atoms to create a change in energy which drives the atoms to the most intense part of the light beam. Lead researcher Philip Light says: “What is really exciting is that now we have the possi­bility to do quantum experiments on these trapped atoms. Our first experiments intend to use these stored atoms as elements of a quantum memory. We hope that our work may eventually form part of absolutely secure communi­cations channel that is of obvious high interest to defence, intel­ligence and industry.”

The researchers are now moving onto the next stage in which the tractor beam is formed from a hollow cone of light rather than a solid beam of light. In this new confi­guration the atoms will be held at the centre of the light cone where it is perfectly dark. “This is an extremely powerful idea – we can move and mani­pulate the atoms, but are able to shield the atoms from the dis­ruptive effect of intense light,” says Light. The researchers have essen­tially created a quantum funnel which allows them to guide and trap atoms for longer without dis­rupting their delicate quantum state.

IPAS Director Andre Luiten says: “Our researchers are mani­pulating and measuring indi­vidual atoms and molecules to sense the world around us. This new era of quantum sensing is opening up diverse new possi­bilities from attemp­ting to detect disease through finding parti­cular molecules in the breath, to assis­ting miners and defence by detecting ano­malous magnetic fields asso­ciated with mineral deposits or covert submarine acti­vity.” (Source: Univ. Adelaide)

Reference: A. P. Hilton et al.: High-efficiency cold-atom transport into a waveguide trap, Phys. Rev. Applied 10, 044034 (2018); DOI: 10.1103/PhysRevApplied.10.044034

Link: Institute for Photonics and Advanced Sensing, University of Adelaide, Adelaide, Australia

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