Quantum networks need a mediator between storage — spin — and carrier — light. No single molecule had ever pulled off such a feat. But now physicists have found a solution. They placed a carbene molecule into a crystal and cooled it to -269°C. Using optical measurements, they saw that the molecule emits single photons for over an hour, and its spin — a magnetic property — preserves its state for tens of milliseconds. So the molecule became a bridge: one pillar in the world of light, the other in the world of matter.
Even though the molecule is ten thousand times thinner than a hair, it holds a quantum connection longer than many solid-state defects. Astoundingly, this bridge of carbon and hydrogen works more reliably than complex artificial crystals. And most importantly, such bridges can be chemically designed, like building blocks, tailored to any task. Chemical assembly is cheap and precise, unlike the laborious growth of crystals with defects. Perhaps they will become the foundation of the quantum internet.
A single carbene molecule — made only of carbon and hydrogen — is ten thousand times thinner than a hair, yet its spin stores a quantum state hundreds of times longer than many atomic defects.
The data exchange between molecule and light echoes sci-fi tales of quantum communicators.