NIST’s Quantum Logic Clock Returns to Top Performance
NIST physicists have upgraded their quantum logic clock, an experimental atomic clock based on a single aluminum ion, achieving the best performance of any clock worldwide. The clock’s systematic uncertainty is now 9.4×10−19, meaning it would neither gain nor lose a second in 33 billion years – about two-and-a-half times the age of the universe. This makes it the world leader in precision but not stability compared to NIST’s other lattice clocks.
The quantum logic clock borrows logical decision-making techniques from experimental quantum computing. Aluminum is an exceptionally stable source of clock ticks, vibrating between two energy levels over a million billion times per second. However, its properties are not easily manipulated or detected with lasers, so logic operations with a partner magnesium ion are used to cool the aluminum and signal its ticks.
NIST scientists are working on several different types of experimental clocks, each based on different atoms and offering its own advantages. All these experimental clocks are based on optical frequencies, which are higher than the microwave frequencies used in today’s timekeeping standards based on cesium. The improved performance of the logic clock was enabled by a new ion trap design that reduced heat-induced ion motion, improved quantum control, and a lower frequency used to operate the ion trap.
The clock’s precision was determined by measuring and adding up the frequency shifts caused by nine different effects. Stability was measured by comparison to NIST’s ytterbium lattice clock. Additional improvements in trap design and other features are planned to further improve performance. Already, NIST’s three experimental clocks can be compared to improve measurements of possible changes in some of the fundamental “constants” of nature, a line of inquiry that has important implications for cosmology and tests of the laws of physics such as Einstein’s theories of special and general relativity.
Source: https://www.nist.gov/news-events/news/2019/07/nists-quantum-logic-clock-returns-top-performance
Keywords: Aluminum, Ion, Clock
