A BGA ion trap (center) atop a 1 cm2 interposer chip and a ceramic pin grid array carrier" (credit: D. Youngner, Honeywell Inc)A team from Georgia Tech Research Institute and Honeywell International in the US have developed an ion trap architecture that could help to increase the density of quantum bits (qubits) in quantum computing. Their approach uses a new microfabrication technique that allows more electrodes to be placed on a surface trap chip while wiring them from the back of the chip in a compact and scalable way, at the same time maintaining the required laser access.
As quantum computers have generally been constrained by an inability to increase the number of qubits that encode, store and access large amounts of data, increasing their densities could lead to simulation of the interactions of complex molecules to a much greater detail than currently possible in classic computing, boosting research in chemistry, biology and material science. The ion trap microfabrication is also relevant for the production of miniature atomic devices such as sensors, magnetometers and chip-scale atomic clocks.
“Our vision is to turn this into a miniaturized, robust, and nicely packaged system suitable for commercialization, which requires solving a host of engineering problems.”Nicholas Guise
Quantum computers use qubits to store information, a process that involves quantum superposition – the qubit is roughly in a combination of 0 and 1, allowing for much more information to be encoded. Experimentally, the challenge has been to develop controllable physical systems that can serve as qubits, and here they chose individual ions trapped inside a vacuum chamber, with the qubits then being then manipulated by laser.
As reported in the Journal of Applied Physics [Guise et al. J. Appl. Phys. (2015) DOI: 10.1063/1.4917385], the team developed and tested this new architecture built around ball-grid array (BGA) connections, fabricating traps with nearly 100 electrodes on the surface of a chip a few square millimeters in size. The main feature of BGA is providing electrical signals directly from the reverse of the mount to the surface, thereby increasing the potential density of electrical connections. They were also able to free up further space by replacing area-intensive surface or edge capacitors with trench capacitors and strategically moving wire connections. The approach meant they could tightly focus an addressing laser beam for speedy operations on single qubits.
However, using trapped ion qubits needs a great deal of bulky equipment and many staff, making it crucial to miniaturize both the electronics and the optics of the device, a task the team is continuing to work on. As study leader Nicholas Guise said, “Our vision is to turn this into a miniaturized, robust, and nicely packaged system suitable for commercialization, which requires solving a host of engineering problems.”