Qutech and Intel jointly designed a qubit-controlling chip destined to solve the quantum computer’s wiring bottleneck. Currently, each qubit in a quantum computer is addressed individually, by a single wire. “This stands in the way of a scalable quantum computer since millions of qubits would require millions of wires,” explains lead investigator Lieven Vandersypen of Qutech. The solution: taking the control unit inside the cryogenic vessel, where the qubits reside.
Researchers and engineers from Qutech and Intel, therefore, designed a control chip that can withstand the extreme cold. Named Horse Ridge after the coldest place in Oregon, the CMOS IC is based on Intel’s 22nm low-power FinFET technology. “As electronic devices operate very differently at cryogenic temperatures, we used special techniques in the chip design both to ensure the right chip operation and to drive the qubits with high accuracy,” says co-lead investigator Edoardo Charbon.
Ultimately, the controller chip and the qubits can be integrated on the same die (as they’re all fabricated in silicon) or package, thus further relieving the wiring bottleneck.
To assess the quality of the Horse Ridge chip, it was compared to a classical room-temperature controller. It turns out the gate fidelity of the system is very high (99.7 percent) and limited not by the controller but by the qubits themselves. Next, the controller’s programmability was showcased using the Deutsch-Jozsa quantum algorithm, which is one of the simplest algorithms that’s much more efficient on a quantum computer than on a traditional computer. This demonstrated the ability to program the control chip with arbitrary sequences of operations and opens the way to on-chip implementation and a truly scalable quantum computer.