University of Adelaide researchers have created a highly efficient waveguide trap for atoms that could be used for experiments in quantum memory. The trap, or tractor beam, is made of IR light that interacts with the atoms to create a change in energy that drives the atoms to the most intense part of the light beam. The beam captures the atoms and pulls them into a microscopic hole at the center of an optical fiber. The atomic chamber in which atomic tractor beams were created. Courtesy of the Institute for Photonics and Advanced Sensing. “Every atom that enters the tractor beam is pulled into the fiber — there is no escape,” said researcher Ashby Hilton. “And once sucked into the interior of the optical fiber, 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.” Using their atom-guiding technique, researchers were able to load 3 × 106 cold rubidium atoms into a hollow-core optical fiber — an order-of-magnitude greater than previously reported results. This result was possible, said the researchers, because it was guided by a physically realistic simulation that could provide the specifications for a loading efficiency of 3 percent and a peak optical depth of 600. The researchers observed the real-time effects of light-assisted cold-atom collisions and background-gas collisions by tracking the dynamics of the cold-atom cloud as it fell into the optical fiber. In the next stage of the experiments, the tractor beam will be 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 center of the light cone where it is perfectly dark. The cone configuration will allow the researchers to guide and trap atoms for a longer period of time without disrupting their quantum state. Researcher Philip Light with the atomic chamber in which the atomic tractor beams were created. Courtesy of the Institute for Photonics and Advanced Sensing. “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,” said researcher Philip Light. The new waveguide trap could open the way for quantum experiments that the researchers believe could lead to new secure communications or advanced sensing technologies. “What is really exciting is that now we have the possibility to do quantum experiments on these trapped atoms,” said Light. “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 an absolutely secure communications channel that is of obvious high interest to defense, intelligence, and industry.” The research was published in Physical Review Applied (https://doi.org/10.1103/PhysRevApplied.10.044034). These are experimental and simulated movies of atoms being optically guided into a hollow-core photonic crystal fiber (HC-PCF). The cloud of 100 million atoms at 3 uK is released from the magneto-optical trap (MOT) and falls under gravity. Atoms within the optical dipole trap with low enough energy are guided into the hollow core fiber, generating extremely large optical depths. Courtesy of P. Light, A. Hilton, and the Institute for Photonics and Advanced Sensing.