NIST Researchers Achieve Near-Perfect Control of Molecular Ion

USA: NIST Researchers Achieve Near-Perfect Control of Molecular Ion

Physicists at the National Institute of Standards and Technology (NIST) have demonstrated high‑fidelity quantum state control of a calcium monohydride molecular ion, publishing their findings in Physical Review Letters on December 9, 2025. The experiment was conducted in NIST’s Ion Storage laboratory in Boulder, Colorado, and aims to expand quantum‑technology capabilities beyond single atoms by leveraging the richer internal structure of molecules.

Molecular Complexity and Control Challenges

Unlike single atoms, which present a relatively simple, spherical shape, molecules such as calcium monohydride possess rotational and vibrational degrees of freedom that make them highly sensitive to environmental changes. “If you’re sensitive to something, it can be a curse, because you would like to not be sensitive, or it can be a blessing,” explained NIST physicist Dietrich Leibfried. This sensitivity, while useful for sensing applications, has historically hindered precise manipulation.

Quantum Logic Spectroscopy Technique

The team employed quantum logic spectroscopy, a method originally developed for ion‑based atomic clocks. A singly charged calcium ion served as a “helper” ion, co‑trapped with the calcium monohydride ion. By laser‑cooling the calcium ion, the researchers indirectly cooled the molecular ion, reducing its motion and allowing the laser to address the molecule’s rotational states. Changes in the molecule’s rotation were inferred from brief photon flashes emitted by the helper ion.

Experimental Results

Repeated measurements showed a 99.8% success rate in driving the molecule between quantum states, meaning roughly 998 out of 1,000 attempts succeeded. The rotational state remained stable for about 18 seconds before thermal radiation induced a transition, offering thousands of measurement opportunities within a single trial. The cold environment extended the molecule’s coherence time to roughly ten times longer than at room temperature.

Implications for Quantum Technologies

Because the molecular ion acted as an exceptionally sensitive thermometer, the researchers suggest it could improve the thermal management of atomic clocks, which are vulnerable to minute temperature fluctuations. Moreover, the protocol is not limited to calcium monohydride; the same approach could be adapted to a wide variety of charged molecules, potentially broadening the toolbox for quantum computing, precision sensing, and fundamental physics investigations.

Future Directions

Baruch Margulis, a postdoctoral fellow on the project, emphasized that the work demonstrates a versatile protocol rather than a one‑off experiment. “When you think about a periodic table, it has a finite number of elements. Molecules are more diverse. So, although they are hard to control, there’s a huge pool of molecules,” he said. The team plans to explore control of more complex species and to integrate molecular qubits into larger quantum‑information architectures.

This report is based on information from NIST, licensed under Public Domain (U.S. Government Work). Source: Official U.S. Government release.