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Increased control over ions’ motions may help improve quantum computers

A single ion was put into quantum states with up to 100 quanta of energy

11:00am, July 22, 2019
physicist laser beryliium ion

ION MANEUVERS  Physicist Katie McCormick (shown manipulating a mirror that directs a laser beam) and colleagues coaxed a beryllium ion to go through the motions. The ion exhibited precise quantum movements within an electromagnetic field.

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Physicists are taking their quantum powers to the next level — the next energy level, that is.

Researchers have controlled the motion of a trapped ion, an electrically charged atom, better than ever possible before, manipulating the energy level of its oscillation within an electromagnetic field. A single ion of beryllium, trapped by electromagnetic fields, was made to oscillate according to scientists’ bidding, the team reports July 22 in Nature.

In quantum mechanics, energy comes in discrete amounts, packets known as quanta. Using lasers to tweak the ion, the researchers were able to set it oscillating within the electromagnetic field that confined it, with any number of quanta up to 100, breaking previously published records of about 17 quanta.

The team also put the ion in a superposition — a weird situation in which the ion is simultaneously in two energy states at once, making it ultrasensitive to any stray electromagnetic fields. The larger the difference in the two energy levels in superposition, the more sensitive the ion is. The researchers put the ion in a superposition between a state with no quanta of energy and one with 18. Such ions could be used as precise sensors to locate electromagnetic fields.

Scientists’ newly demonstrated prowess with ions could also be used to build better quantum computers. Some quantum computers store and process information via ions confined in traps, with lasers used to perform operations on the quantum data. Though quantum computers are still in their early stages, scientists predict the machines will be able to perform calculations more complex than what’s currently possible (SN: 7/8/17, p. 28).

“It’s an unprecedented level of control,” says Katie McCormick, a physicist at the University of Washington in Seattle. “We’ve generated quantum states at a level that nobody has before.”


K.C. McCormick et al. Quantum-enhanced sensing of a single-ion mechanical oscillator. Nature. Published online July 22, 2019. doi: 10.1038/s41586-019-1421-y.

Further Reading

E. Conover. Quantum computers are about to get real. Science News. Vol. 191, July 8, 2017, p. 28.

L. Sanders. Minifridge makes quantum computers last. Science News Online, August 6, 2009.

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