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When it comes to quantum computing, two atoms are better than one. For the first time, researchers have made a molecule simply by pressing two atoms together and making them bond on command. Molecules like the one they built could be used to store and process information in quantum computers.

Most chemical reactions are done by mixing large quantities of different types of atoms together with a catalyst to make them react. This method is imprecise, though, and makes it difficult to get one specific molecule exactly how and where you want it, or to study any individual reaction in detail.

鈥淲e鈥檙e building a new molecule by putting together individual atoms like blocks of Lego, rather than traditional chemistry where we just throw a lot of things together and hope for a reaction,鈥� says at Harvard University. 鈥淵ou end up with exactly one molecule exactly where you want it to be.鈥�

Liu and his colleagues used optical tweezers 鈥� highly focused laser beams that move atoms around 鈥� to control a sodium atom and a caesium atom. They pointed the lasers at the same spot to join the two ultracold atoms together into a single tweezer. Finally, they shone an additional laser tuned to a resonant frequency, which bound the two atoms together.

Taking a spin

The result was a single molecule of sodium and caesium, NaCs, which is highly asymmetrical because caesium is so much bigger than sodium. That asymmetry allows the molecules to rotate, making them potentially useful for quantum computing.

In quantum computers, information is stored in quantum bits, or qubits. A good qubit has two important qualities: it does not change its quantum state due to environmental noise like slight changes in temperature, and it can interact with other qubits to communicate. Those qualities are often in direct conflict.

Not so in this case, Liu says. If his custom molecules are made to rotate quickly, it鈥檚 tough for environmental noise to change that rate of rotation. Their asymmetrical magnetic field makes them behave like tiny bar magnets, so two placed near one another do not have to touch to exchange rotational energy.

鈥淎ll I have to do is put two molecules together that are rotating at similar speeds, and then they鈥檒l be able to affect each other鈥檚 quantum states, and that鈥檚 how you do the computing,鈥� says Liu.

The NaCs molecules that Liu and his team have made will not be useful as qubits quite yet聽鈥� they鈥檙e not bound together strongly enough. But Liu says that within the next year the team hopes to make the bonds tighter by reducing vibrations in the system with lasers, and then these bespoke molecules can be put to work.

Read more: This qubit redesign may make it easier to make quantum computers