NIST Unveils World’s Most Accurate Clock: A Quantum Leap in Timekeeping

American scientists have set a new benchmark in precision timekeeping: researchers at the National Institute of Standards and Technology (NIST) have developed the most accurate clock in the world. This groundbreaking device operates using a single aluminum ion, confined within an electromagnetic trap. Far surpassing conventional optical systems, the clock achieves a measurement precision of 19 decimal places—an unprecedented feat in the field of chronometry.

Yet it is not merely the extraordinary accuracy that sets this clock apart, but its remarkable stability. The new apparatus is 2.6 times more resilient to noise than previous ion-based timekeepers. This leap forward was made possible through a meticulous redesign of the entire system—from the geometry of the trap and the properties of its coating to the configuration of the vacuum chamber and the integration of its optical components. In terms of precision, the system outperformed the previous world record by 41%.

The aluminum ion proves to be an ideal candidate for ultra-precise measurements due to its stable oscillation and minimal sensitivity to external disturbances such as temperature shifts and magnetic interference. However, it presents significant challenges for direct laser cooling and detection. To circumvent this, researchers introduced a companion ion—magnesium.

This method, known as quantum logic spectroscopy, leverages the manageability of magnesium to cool the aluminum ion, synchronize its motion, and relay its quantum state. In essence, data is read through the behavior of the magnesium ion, sidestepping the difficulties of direct interaction with aluminum. This clever design allows scientists to exploit aluminum’s advantages without being hindered by its limitations.

Even with this synchronization, the system encountered several technical hurdles. One significant issue involved excess micromotion of the ions due to asymmetric electric fields—an invisible yet disruptive factor affecting signal stability. To address this, the team reinforced the trap’s base with a diamond substrate and reconfigured the gold plating on its electrodes, effectively eliminating the distortions and stabilizing the ion environment.

The vacuum chamber, too, required a major overhaul. The prior stainless steel enclosure released hydrogen molecules that interfered with the ions, disrupting their behavior and necessitating frequent system resets. The new titanium chamber reduced residual hydrogen levels by a factor of 150, enabling continuous operation for several days—in contrast to the 30-minute intervals previously required for recalibration.

The laser system, crucial for reading ion oscillations, remained one of the most sensitive components. In 2019, it required weeks of averaging to suppress frequency fluctuations. This challenge was overcome with the help of Jun Ye’s laboratory at JILA—a joint institute of NIST and the University of Colorado Boulder—home to one of the most stable lasers in existence.

A signal from the JILA laser was transmitted via a 3.6-kilometer fiber-optic link laid beneath city streets and synchronized with the aluminum ion clock using an optical frequency comb—a tool that serves as a spectral ruler. This integration transferred the reference laser’s stability directly into the operational system.

Following these refinements, the team succeeded in sustaining the ion’s excited state for an entire second, compared to just 150 milliseconds previously. This enhancement reduced the time required for ultra-precise measurements from several weeks to just one and a half days.

Beyond setting a new standard of precision, this clock has evolved into a robust platform for quantum experimentation. Its architecture lends itself to testing novel configurations, including multi-ion systems and entangled states—ushering in new possibilities for advanced quantum logic and precision metrology.

Moreover, this advancement brings the global scientific community closer to redefining the second. Next-generation atomic clocks like this one can detect geophysical phenomena—such as gravitational potential differences at varying altitudes—with previously unthinkable accuracy. They may even enable tests to determine whether the fundamental constants of physics change over time.