Matter shines light on quantum data interface at NIST

The National Institute of Standards and Technology (NIST) says it has developed a new way of reading data in a quantum computing. This paves the way for a light-matter quantum interface, making for much more efficient quantum data processing.

The design shows it is possible to develop a system that could pair a single photon with a single ion. This would create an information interface between light and matter quantum bits (qubits): for example, the spins of individual ions could be transferred to the field orientations of individual photons, which in turn could be transported to other parts of a quantum computer network.

The paper, to be published in Physical Review Letters, describes a 1-millimetre-square ion trap with a built-in optical fibre. Postdoctoral researcher Aaron VanDevender says: "The design is helpful because of the tight coupling between the ion and the fiber, and also because it's small, so you can get a lot of fibers on a chip."

In the announcement, NIST says: “ Light emitted by an ion passes through a hole in an electrode and is collected in the fiber below the electrode surface. By contrast, conventional ion traps use large external lenses typically located 5 centimetres away from the ions—about 500 times farther than the fibre—to collect the fluorescence light.”

Although the optical fibre doesn't capture as much light as a lens, this doesn't matter because the ions are extremely bright, so it is good enough to get the data needed for a quantum computer. Shaping the tip of the fibre and using special anti-reflective coatings will boost efficiency, and the team notes that multiple fibres could be built into a single trap, making it potentially much better at handling large numbers of ions.