In this published advancement, the world’s most precise time is now measured in laboratories of the National Institute of Standards and Technology (NIST) in the USA. A new optical atomic clock based on an aluminum ion exhibits an extremely narrow frequency uncertainty, indicating that the amount of time to shift a second forward or backward is so long that it cannot be compared to the age of the universe. The fractional frequency uncertainty is around an impressive level of 5.5 × 10−19, providing an unprecedented stability level, such as 0.0….
Two key criteria highlighted in the measurement, accuracy and stability, define the success of this clock. While accuracy refers to how close the measured time is to the actual time; stability indicates reproducibility and consistency. This international standard was made possible through years of improvements in advanced components such as lasers, ion traps, and vacuum chambers.
As stated by the lead author of the study, Mason Marshall,
“Working on the most precise clock ever made is truly exciting,” this is demonstrated in tests carried out with the 27Al+ aluminum ion and the 25Mg+ magnesium ion, which plays a critical role in their interaction. The impressive aspect of Q timeless is the suitability of the aluminum ion for timing; however, due to laser-controlled challenges, the magnesium ion takes over to perform cooling and quantum state readout by intervening.
The most significant step in this improved clock was extending the Rabi probe duration to 1 second. This was achieved by transmitting the laser stability of the cryogenic silicon resonator used in Jun Ye’s laboratory via a 3.6-kilometer fiber link to NIST, reducing the instability levels previously observed by a factor of three. Additionally, the team redesigned the ion trap to minimize timing errors caused by microscopic movements. Electrodes reinforced with diamond plates and gold coatings increased the trap’s stability; the vacuum chamber was reconstructed with titanium, reducing hydrogen gas levels by approximately 150 times. These modifications allowed the clock to operate for days without needing to reload the ions.
As a result, this development allows the clock to maintain its precision to 19 digits over 36 hours; previous versions required about three weeks to achieve the same accuracy. Such a development could make it possible to define a second much more reliably and precisely, and could also offer new opportunities to test the foundational constants of the universe for their true constancy levels.
