Tackling qubit connectivity in quantum computers
Quantinuum has developed a digital bus-based approach to connect qubits in quantum computers rather than using direct connections that don’t scale.
The new connectivity scheme is being adopted for the Quantinuum H3 quantum computer being developed by Honeywell with a new 2D grid for trapped ion qubits.
At the moment each qubit in a quantum computer needs its own set of individual control signals, sometimes up to 20. This limits the ability of architectures to scale, particularly with ion trap qubits.
The wiring problem has been diagnosed by every major manufacturer of quantum computers as a key challenge, says Quantinuum, and overcoming it will be recognized as one of the most critical milestones on the road to useful quantum computing.
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Quantinuum’s patented design only solves the wiring problem but also demonstrates trapping and control of a large number of qubits on a grid-based trap. The work reduces the number of wires per ion from 20 to 1 using a fixed bus of wires that doesn’t scale with the number of qubits.
This allows Quantinuum’s next generation quantum computer systems using the Quantum Charge-Coupled Device (QCCD) architecture to use a fixed number of control signals, alongside one switch per qubit. The switches are far easier to miniaturize and fabricate using techniques from classical computing, making them much more favourable for scaling and reduces the number of independent signals from 20 to 1.
The 2D grid enables easier and faster qubit rearrangement. It is also the first demonstration of a chip that can trap and control large numbers of trapped-ion qubits at once.
With this design, the majority of the connections would be digital rather than analog, and there are several projects to develop CMOS digital chips that can operate in the very low temperatures around -273K that the ion trap devices operate at.
Three distinct demonstration systems show the reproducibility and commercial viability of this approach. By minimizing the control complexity, this approach also simplifies the interface between quantum and classical systems, accelerating the development of hybrid quantum algorithms.
“This is a significant milestone not only for Quantinuum but for the entire quantum industry, propelling us into an era of widespread quantum commercialization,” said Nash Palaniswamy, Chief Commercial Officer of Quantinuum. “Our team’s groundbreaking work paves the way for building larger and more powerful quantum computers, enabling businesses to harness the transformative power of this technology and unlock real-world solutions across various sectors.”
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