The world's best atomic clock has become even more accurate, neither gaining nor losing a second over 15 billion years — longer than the age of the Universe.
The clock keeps time using 2,000 ultracold strontium atoms trapped in a laser lattice. Its pendulum is a laser that has a frequency tuned to resonate with that of the photons that are released and absorbed by the atoms as they switch between two energy states. By using a more stable laser and by reducing the effects of environmental perturbations, Jun Ye at the JILA institute in Boulder, Colorado, and his team made the 'ticks' of the timepiece more uniform. This increased the clock's accuracy by three times compared with the previous record.
The result brings strontium-based optical clocks closer to replacing the current standard for time measurement, the caesium fountain clock, which makes lower-frequency atomic transitions.