Diamond clock slashes temperature drift
Researchers from the U.S. and Germany have developed a diamond-based atomic clock that reduces temperature-induced frequency drift by roughly an order of
A research team from the United States and Germany has published a method to dramatically reduce the temperature sensitivity of diamond-based atomic clocks. Their work, appearing in the journal Physical Review Applied on August 28, 2026, combines signals from two quantum transitions to cut long-term thermal drift by approximately tenfold.
Most natural diamonds contain crystallographic defects. A common and useful impurity is the nitrogen-vacancy (NV) center, where a nitrogen atom replaces a carbon atom next to an empty lattice site. These NV centers possess electron and nuclear spin states that can be manipulated with light and microwaves, forming the basis for a solid-state clock. Such clocks promise robustness and easier integration with electronics compared to systems that trap atoms. However, the primary clock transition in these centers is notoriously sensitive to thermal fluctuations.
The Problem of Thermal Sensitivity
The standard clock signal for an NV center comes from a ground-state electron spin splitting, a quantity the researchers label D, which is 2.87 GHz. This D-only transition has a temperature sensitivity of 25.3 parts per billion per millikelvin. Even minor temperature shifts can therefore destabilize the clock's frequency, making it unsuitable for precise timekeeping without compensation.
The team identified a second, less temperature-sensitive signal within the same defect. The 14N nucleus at the heart of the NV center has a quadrupole splitting, labeled Q, of about 4.94 MHz. This splitting arises from the interaction between the nucleus's electric quadrupole moment and the local electric field of the crystal.
A Composite Frequency Reference
By measuring both the D and Q transitions simultaneously, the scientists created a composite frequency reference. They applied a 475 Gauss magnetic field aligned with the NV axis. Optical pumping with a laser prepared the electron states, and fluorescence readout measured both the electron and nuclear spin states.
The researchers state this dual-measurement approach reduces the long-term temperature-induced drift by about an order of magnitude for integration times of 1,000 seconds at room temperature. In their tests, the new diamond clock prototype ran for 10 days alongside a standard rubidium vapor-cell clock for comparison.
The performance data, as reported in the source, shows the following improvements in fractional instability over the simpler rubidium D frequency clock:
| Average Time (seconds) | Diamond Clock Instability | Improvement Factor vs. Rubidium Clock |
|---|---|---|
| 200 | Below 5 × 10⁻⁹ | ~4 |
| 200,000 (2.3 days) | Below 1 × 10⁻⁸ | ~200 |
"We find that temperature is no longer the dominant source of instability," the researchers write. Their demonstration points toward compact, multifunctional solid-state quantum sensors and clocks where thermal management is less critical. The work was authored by Sean Lourette and colleagues.
