3D-printing could make it easier to make large quantum computers

To make some quantum computers larger, and therefore more powerful, we may have to 3D-print them.

Currently, there is no consensus on the single best design for quantum computers, but researchers agree that to become unambiguously useful, quantum computers will have to be made larger. For those that use ions as quantum bits, or qubits, a key building block is called an “ion trap”. Hartmut Häffner at the University of California, Berkeley, and his colleagues have now developed a 3D-printing technique for miniaturised ion traps, which could make it easier to combine many of them into one large computer.

The purpose of an ion trap is right in its name: it confines ions in place and helps control their quantum states with electromagnetic fields, an essential condition for using ions to run calculations.

For their version, the researchers 3D-printed traps that were just a few hundred microns across. In extensive laboratory tests, these beat more conventional designs. They captured ions up to 10 times more efficiently and did so with shorter wait times from when the trap is turned on to when the ions can be used, says Häffner. “You can scale to an order of magnitude more qubits, and you can speed up things,” he says.

Team member Xiaoxing Xia at Lawrence Livermore National Laboratory in California says that 3D-printing is a perfect match for the problem at hand, because it can make small and complex objects with fewer restraints than methods more akin to chip manufacturing. This means the researchers could follow the success of their tiny ion trap with more innovative and novel designs. Team member Shuqi Xu, also at the University of California, Berkeley, says some are already in the works. “3D-printing lets you reimagine things to a large degree,” says Xia.

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The methods currently used to make ion traps “suffer from complexity, inherent limitations and sometimes from low yield, high costs and bad reproducibility. It appears to me that the 3D-printing scheme could eventually overcome all these issues… which is in turn a key prerequisite for scalability quantum computing with trapped ions”, says Ulrich Poschinger at the Johannes Gutenberg University Mainz in Germany.

Xia says the team now wants to integrate optical components into their 3D-printed designs, such as miniaturised lasers that are necessary for quantum computing. Häffner adds that their tiny traps could help redesign mass spectrometers, which are ubiquitous tools in chemistry.