NIST Develops World's Most Accurate Atomic Clock with 19 Decimal Precision

The National Institute of Standards and Technology (NIST) has set a groundbreaking milestone in timekeeping by unveiling the world's most accurate atomic clock, capable of measuring time with an unprecedented precision of 19 decimal places. This advancement, reported on July 16, 2025, represents a 41% improvement over its predecessor and is integral to the latest generation of optical atomic clocks.

The newly developed clock, which utilizes a trapped aluminum ion, showcases remarkable advancements in both accuracy and stability. According to the findings published in the journal *Physical Review Letters*, this clock is not only more accurate but also 2.6 times more stable than any other ion clock currently in existence. Dr. Mark Kasevich, a physicist at Stanford University who specializes in atomic physics, noted, "The precision of this clock has implications that extend beyond timekeeping; it could enhance GPS technology and improve fundamental physics research."

In the realm of atomic clocks, two primary measures are crucial: accuracy and stability. Accuracy refers to how closely a clock can align with the true time, while stability measures the clock's ability to maintain consistent time measurement over periods. The aluminum ion clock excels in both areas, making it a significant advancement over the cesium-based clocks, which have historically defined the second.

The aluminum ion's high-frequency ticking rate provides stability, as it is less sensitive to environmental variables such as temperature fluctuations and magnetic fields. However, achieving this stability has not come without challenges. Researchers faced significant hurdles in probing and cooling aluminum ions using lasers, which are essential for the operation of atomic clocks. To overcome these challenges, the NIST team implemented a novel approach by pairing the aluminum ion with a magnesium ion, which can be easily controlled by lasers. This method, known as quantum logic spectroscopy, allows the magnesium ion to cool the aluminum ion, facilitating the measurement of the clock's state based on its motion.

Moreover, the design of the ion trap played a critical role in the clock's performance. Previous designs caused excess micromotion, which adversely affected accuracy. The team addressed this by redesigning the trap and utilizing thicker diamond wafers and modified gold coatings on electrodes to eliminate electric field imbalances. These improvements reduced ion motion, enabling the clock to tick with unprecedented accuracy.

Upgrades to the vacuum system were also essential in enhancing the clock's functionality. Traditional steel vacuum chambers allowed hydrogen to permeate, disturbing the clock's operation. By redesigning the vacuum chamber using titanium, the team reduced background hydrogen levels by a staggering 150 times. These enhancements have enabled longer experimental runs without the need to frequently reload ions.

The implications of the NIST’s advancements stretch beyond theoretical applications. Dr. Elaine McCarthy, a researcher at the National Aeronautics and Space Administration (NASA), stated, "Such precision can drastically improve satellite navigation and time synchronization across various technologies, including telecommunications and global positioning systems."

As nations and organizations race to develop increasingly precise timekeeping technologies, the NIST clock stands at the forefront of a new era in scientific measurement, promising to drive future innovations in both fundamental physics and practical applications. The ongoing developments in atomic clock technology will likely continue to enrich our understanding of time and its role in various scientific fields, leading to profound advancements in technology and research methodologies.