Intel and QuTech utilized the Horse Ridge chip to demonstrate two-qubit quantum computing capabilities. The researchers say it could pave the way toward silicon-based quantum computing. (Image Credit: Marieke de Lorijn)


Engineers from QuTech in the Netherlands and Intel designed and tested a cryogenic chip that controls qubits operating at very low temperatures. Their design presents new opportunities to solve the "wiring bottleneck," significantly progressing toward a scalable quantum computer.


"Our research results, driven in partnership with QuTech, quantitatively prove that our cryogenic controller, Horse Ridge, can achieve the same high-fidelity results as room-temperature electronics while controlling multiple silicon qubits. We also successfully demonstrated frequency multiplexing on two qubits using a single cable, which clears the way for simplifying the 'wiring challenge' in quantum computing. Together, these innovations pave the way for fully integrating quantum control chips with the quantum processor in the future, lifting a major roadblock in quantum scaling," says Stefano Pellerano, principal engineer at Intel Labs.


A wire individually controls each qubit. "This stands in the way of a scalable quantum computer since millions of qubits would require millions of wires," QuTech's lead investigator, Lieven Vandersypen, says." This is called the 'wiring bottleneck.' In traditional computers, a modern processor with billions of transistors has only a few thousand connections. The cryogenic temperatures at which qubits operate (20 millikelvin, or about -273 degrees Celsius) complicate the use of traditional solutions." Chips cannot withstand extreme temperatures, leading to a newly designed and tested cryogenic chip.


The team designed a special silicon-based integrated circuit that endures temperatures at -454 °F (-270 °C) and addresses qubits. "We exploited the same technology adopted for the conventional microprocessor, the CMOS technology. For Horse Ridge, we specifically used the Intel 22nm low-power FinFET technology." said co-lead investigator Edoardo Charbon, head of EPFL's Advanced Quantum Architecture Laboratory. "As electronic devices operate very differently at cryogenic temperatures, we used special techniques in the chip design both to ensure the right operation and to drive qubits with high accuracy." Diminishing the wiring bottleneck is achieved by integrating a controller chip and qubits on the same die.


The team compared the cryogenic Horse Ridge control chip with a traditional room temperature controller to examine its quality. They discovered that the system's gate fidelity, restricted by the qubits and not the controller, reached 99.99%.

The controller's programmability was demonstrated using the Deutsch-Jozsa two-bit quantum algorithm, which is more efficient on a quantum computer than a traditional one. This allows the control chip to be programmed with arbitrary sequences of operations. It also paves the way toward on-chip integration and a scalable quantum computer. 


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