Researchers used light and microwaves to work with a single molecular qubit at 4.5 kelvin. The cold-lab result could help develop future quantum devices.
One molecule, one quantum bit
Scientists have prepared, controlled and read a quantum bit inside one molecule. Simon Roggors and colleagues reported the experiment in Nature on October 28, 2026. They could study an individual molecule, rather than only the combined signal from a crowd. 1
A quantum bit, or qubit, is a basic unit of quantum information. Here, it uses two states of the molecule's electron spin. Spin is a quantum property that gives electrons magnetic behavior. The two states can also form a quantum combination, called a superposition.
Light finds the molecule
The team used a type of molecule called a carbene. It sat inside a crystal made from molecules with a closely matching shape. This surrounding material helped keep the qubit molecule steady. 1
The researchers used light to turn starting molecules in the crystal into active qubit molecules. Gentle activation and carefully chosen laser light let them pick out individual ones. They checked the emitted light to confirm a single molecule was producing the signal. 1
Laser pulses prepared the spin and helped read its state. Microwave pulses changed it between the laser pulses. So this was not control by light alone. 1
Two different clocks
The experiment worked at 4.5 kelvin, only 4.5 degrees above absolute zero, the lowest possible temperature. It was far colder than a room. 1
The team measured coherence: how long the parts of a quantum superposition keep their needed relationship. With a repeated pattern of protective microwave pulses, the measured coherence time was about 2.2 milliseconds. A millisecond is one-thousandth of a second. This protection was active, not simply a molecule left alone. 1
Another measurement gave a spin relaxation time of about 21 milliseconds. That tracks how the prepared balance between spin states fades. It does not mean the qubit kept its full quantum information for that long. 1
Why it matters
Chemistry lets researchers design a molecule and its surroundings. This study shows that one such molecule can combine access through light with controlled spin changes. That is useful progress toward building molecular quantum devices. 1
But this was not a complete quantum computer. It also did not show quantum links between distant molecules. Those remain goals beyond this cold-lab experiment. 1
Read the research
[1] Roggors and colleagues: A single-molecule spin–photon interface, Nature, October 28, 2026