The wavelike pattern at the top shows the accordion-like structure of a proposed quantum material—an artificial crystal made of light—that can trap atoms in regularly spaced nanoscale pockets. These pockets can be made to hold a large collection of ultracold “host” atoms (green), slowed to a standstill by laser light, and individually planted “probe” atoms (red) that can be made to transmit quantum information in the form of a photon (particle of light). The lower panel shows how the artificial crystal can be reconfigured with light from an open (hyperbolic, in orange) geometry to a closed (elliptical, in green) geometry, which greatly affects the speed at which the probe atom can release a photon. Credit: Pankaj K. Jha/UC Berkeley
Scientists have devised a way to build a “quantum metamaterial” using ultracold atoms trapped in an artificial crystal composed of light. The theoretical work represents a step toward manipulating atoms to transmit information, perform complex simulations or function as powerful sensors. The research team proposes the use of a “lattice” structure, made with laser light to trap atoms in regularly spaced nanoscale pockets. Such a light-based structure, which has patterned features that in some ways resemble those of a crystal, is essentially a “perfect” structure – free of the typical defects found in natural materials.
Researchers believe they can pinpoint the placement of a so-called “probe” atom in this crystal of light, and actively tune its behavior with another type of laser light (near-infrared light) to make the atom cough up some of its energy on demand as a photon which can be absorbed by another probe atom (in the same or different lattice site) as information exchange.
Pankaj K. Jha said, “Now we have control over the speed of the release of a photon, so we can optically process information much faster, and efficiently transfer it from one point to another.” This ability to release a photon at fast rates, and to transmit it with low losses from one atom to another, is a vital step in processing information for quantum computation, which could use an array of these controlled photon releases to carry out complex calculations far more rapidly than is possible in modern computers.
The non-uniform distribution of the ultracold atoms in the artificial crystal is a key to this latest study, said Jha. “It makes the crucial difference for creating a ‘perfectly’ lossless and reconfigurable quantum metamaterial,” he said, allowing the optical structure of the artificial crystal to be reconfigured from an open geometry (hyperbolic-shaped) to a closed one (elliptical) at the same frequency and with ultrafast timing. This controllable shape-change dramatically changes the speed at which a probe atom in the artificial crystal releases a photon.
The latest proposal suggests it is possible to speed up the rate at which a probe atom can emit a photon from nano to picoseconds, ie billionths to trillionths of a second. Also, this process is importantly considered “lossless,” meaning the photons would not lose any of their energy to their surrounding structure as they likely would in a traditional material. This overcomes one hurdle toward quantum computing and information processing. Atoms planted in the artificial crystal could also possibly be induced to hop from one place to another. In this case, the atoms could themselves serve as the information carriers in a quantum computer or be arranged as quantum sensors, Jha said.
The researchers found that rubidium atoms are ideally suited for this study, however barium, calcium and cesium atoms can also be trapped or planted in the artificial crystal, as they exhibit similar energy levels. While the artificial crystal used in the study is described as 1D, Jha said the same approach could be easily extended to create 2D and 3D quantum metamaterial crystal structures out of light.
To realize the proposed metamaterial in an actual experiment, Zhang and Jha said the research team would need to trap several atoms per lattice site in the artificial crystal, and to hold those atoms in the lattice even when they are excited to higher energy states. Zhang said, “Berkeley Lab has been a leader in groundbreaking research in metamaterials, and this work could open new realms of opportunities for quantum light-matter interactions, with enticing applications in quantum information science.” http://newscenter.lbl.gov/2016/05/11/toward-perfect-quantum-metamaterial/
Recent Comments