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A team of researchers has devised a simple way to tune a hallmark quantum effect in graphene—the material formed from a single layer of carbon atoms—by bathing it in light. Their theoretical work, which was published recently in Physical Review Letters, suggests a way to realize novel quantum behavior that was previously predicted but has so far remained inaccessible in experiments."Our idea is to use light to engineer these materials in place," says Tobias Grass, a postdoctoral researcher at the Joint Quantum Institute (JQI) and a co-author of the paper. "The big advantage of light is its flexibility. It’s like having a knob that can change the physics in your sample."

Trey Porto, a NIST physicist and Fellow of the Joint Quantum Institute, spends his days using atoms and lasers to study quantum physics. But even outside of the lab, he views the world as one great physics problem to tackle. So one morning when he spotted some sunlight dancing across his wall, he couldn’t help but dive in and calculate its movements. He then took his project a step further and began constructing a sundial. Emily sat down with Porto to hear about his clock-making hobby and how today’s time-keeping differs from its ancient counterparts. This episode of Relatively Certain was produced by Emily Edwards and Chris Cesare. It features music by Dave Depper and Poddington Bear. Relatively Certain is a production of the Joint Quantum Institute, a research partnership between the University of Maryland and the National Institute of Standards and Technology, and you can find it on iTunes, Google Play or Soundcloud.

Two independent teams of scientists, including one from the Joint Quantum Institute, have used more than 50 interacting atomic qubits to mimic magnetic quantum matter, blowing past the complexity of previous demonstrations. The results appear in this week’s issue of Nature.As the basis for its quantum simulation, the JQI team deploys up to 53 individual ytterbium ions—charged atoms trapped in place by gold-coated and razor-sharp electrodes. A complementary design by Harvard and MIT researchers uses 51 uncharged rubidium atoms confined by an array of laser beams. With so many qubits these quantum simulators are on the cusp of exploring physics that is unreachable by even the fastest modern supercomputers. And adding even more qubits is just a matter of lassoing more atoms into the mix. 

Computers based on quantum physics promise to solve certain problems much faster than their conventional counterparts. By utilizing qubits—which can have more than just the two values of ordinary bits—quantum computers of the future could perform complex simulations and may solve difficult problems in chemistry, optimization and pattern-recognition.But building a large quantum computer—one with thousands or millions of qubits—is hard because qubits are very fragile. Small interactions with the environment can introduce errors and lead to failures. Detecting these errors is not straightforward, since quantum measurements are a form of interaction and therefore also disrupt quantum states. Quantum physics presents another wrinkle, too: It’s not possible to simply copy a qubit for backup.Scientists have come up with clever ways to detect errors and keep them from spreading. But so far, a complete error detection protocol has not been tested in experiments, partly due to the difficulty of creating controlled interactions between all of the necessary qubits.Now, in a recent article published in Science Advances, researchers at the Joint Quantum Institute tested a full procedure for encoding a qubit and detecting some of the errors that occur during and after the encoding. They applied a scheme that distributed the information of one qubit among four trapped ytterbium ions—themselves also qubits—using a fifth ion qubit to read out whether certain errors had occurred. Ions provide a rich set of interactions, which allowed scientists to link the fifth ion qubit with the other four at will—a common requirement of error detection or correction schemes. With this approach, the scientists detected nearly all of the single-ion errors, performing more than 5000 runs of the full encoding and measurement procedure for a number of different quantum states. Additionally, the encoding itself didn’t appear to introduce errors on multiple ions at the same time, a feature that could have spelled doom for error detection and correction in ions.Although the result is an early step toward larger quantum memories and quantum computers, the authors say it demonstrates the potential of qubit protection schemes with trapped ions and paves the way toward error detection and eventually error correction on a larger scale.Written by Nina Beier