The Ion That Paused for Half a Minute express
A glowing dot in a vacuum chamber refuses to go out, even though the light source has long been switched off. A single ytterbium ion, held by electric fields, is stuck in an excited state, as if the electron inside it has forgotten how to return to its usual place. Normally, such states last milliseconds, but here we are counting seconds.
Physicists at the U.S. National Institute of Standards and Technology made the ytterbium ion absorb light at a wavelength of 377.5 nanometers, sending it into one of its long-lived states. To pinpoint the moment of decay, they kept a second, cooling ion nearby: it soaked up excess heat and allowed them to observe the first ion without interference. They found that one state lives 0.92 seconds, another nearly 10 seconds, and a third, it seems, more than 30 seconds. For comparison: in 30 seconds, light can circle the Earth eight times.
Such long-lived states are a boon for quantum technologies. They can serve as memory cells: write information into an ion and don't worry about it vanishing in an instant. They are also useful in optical clocks — the most precise instruments that measure time by the oscillations of light. The longer a state lives, the more precisely its energy can be measured. Perhaps these very ions will become the heart of future quantum computers and navigation systems.
Original abstract
as written by the authors arXiv:2603.04250
We study the occurrence of long-lived metastable states in the 4f$$^{13}$$5d6s electron configuration of Yb$$^+$$. By optical pumping of a single trapped ion on the $$^2F^\text{o}_{7/2}\rightarrow (7/2,0)_{7/2}$$ transition at 377.5 nm, we prepare a wide range of metastable electronic states. We use a co-trapped control ion to sympathetically cool the spectroscopy ion, allowing us to accurately time its subsequent decay. We record a strong decay signal corresponding to a lifetime of 0.92(8) s, a weaker decay signal with lifetime 9.8(+2.9, -2.0) s, and find evidence for a much longer lifetime, $$>$$ 30 s. We identify the metastable states with these lifetimes qualitatively, and corroborate our results with atomic structure calculations that support the observed lifetimes and decay paths. These long-lived states provide new opportunities in qubit and qudit state detection and optical clocks.
A trapped ytterbium ion is visible to the naked eye: it scatters laser light like a tiny star.
In the series 'The Expanse', quantum computers based on trapped ions control ships and stations.