Rethinking the quantum chip | ScienceDaily

Unlike typical quantum chip designs in which information-processing qubits are placed on a two-dimensional grid, the Cleland Lab team designed a modular quantum processor that includes a reconfigurable router that serves as a central hub. This enables any two qubits to connect and become entangled, whereas in older systems qubits could only communicate with the qubit that was physically closest to them.

“Quantum computers don’t necessarily compete with classical computers on things like memory size or CPU size,” said Andrew Cleland, a professor of PME at the University of Chicago. “Instead, they take advantage of a fundamentally different scaling ratio: combining classical computers with Doubling the computing power requires twice the size of the CPU, or doubling the clock speed requires only one additional qubit.”

The design draws inspiration from classic computers, clustering qubits around a central router, similar to how personal computers communicate with each other through a central network hub. Quantum “switches” can connect and disconnect any qubit in nanoseconds, enabling the generation of high-fidelity quantum gates and quantum entanglement, a fundamental resource for quantum computing and communications.

“In principle, there is no limit to the number of qubits that can be connected through a router,” said Wu Xuntao, a PME doctoral student at the University of Chicago. “If you want more processing power, you can connect more qubits, as long as they fit a certain of floor space.”

Wu is the first author of a new paper published Physical ReviewX It describes this new method of connecting superconducting qubits. The researchers’ new quantum chip is flexible, scalable and as modular as the chips found in phones and laptops.

“Imagine you have a classic computer with a motherboard that integrates many different components, such as a CPU or GPU, memory and other components,” Wu said. “Part of our goal is to transfer this concept to the quantum realm.”

size and noise

Quantum computers are highly advanced yet sophisticated devices that have the potential to transform fields such as telecommunications, healthcare, clean energy and cryptography. Before quantum computers can solve these global problems to the greatest extent possible, two things must happen.

First, they must scale to a sufficiently large size and have flexible maneuverability.

“Such scaling could provide solutions to computational problems that classical computers simply cannot solve, such as factoring huge numbers to crack encryption codes,” Cleland said.

Second, they must be fault-tolerant, able to perform massive computations with few errors, ideally exceeding the processing capabilities of current state-of-the-art classical computers. The superconducting qubit platform being developed here is a promising way to build quantum computers.

“A typical superconducting processor chip is square on which all the qubits are fabricated. It is a solid-state system on a planar structure,” said co-author Haoxiong Yan, who graduated from the University of Chicago PME in the spring , now works as a quantum engineer at Applied Materials. “If you can imagine a two-dimensional array, like a square lattice, that’s the typical topology of a superconducting quantum processor.”

Typical Design Limitations

This typical design results in several limitations.

First, placing qubits on a grid means that each qubit can only interact with at most four other qubits—its immediate neighbors to the north, south, east, and west. Larger qubit connections often enable more powerful processors in terms of flexibility and component overhead, but the four-neighbor limit is often considered inherent to planar designs. This means that for practical quantum computing applications, scaling devices with brutal force may result in unrealistic resource requirements.

Second, nearest neighbor connectivity in turn limits the classes of quantum dynamics that can be achieved and the degree of parallelism that a processor can perform.

Finally, if all qubits are fabricated on the same planar substrate, this poses a significant challenge to manufacturing yields, as even a small number of faulty components means the processor will not function.

“To perform practical quantum computing, we need millions or even billions of qubits, and we need to make everything perfect,” Yan said.

Rethinking the chip

To solve these problems, the team modified the design of the quantum processor. This processor features a modular design that allows different components to be pre-selected before being installed on the processor motherboard.

The team’s next steps are to investigate how to scale quantum processors to more qubits, looking for new protocols to extend the processor’s capabilities and possibly finding ways to connect router-connected clusters of qubits, like a supercomputer. Link its component handlers the same way.

They also hope to extend the distance over which qubits can become entangled.

“Currently, the coupling range is in the mid-range, on the order of millimeters,” Wu said. “So if we’re trying to think about ways to connect remote qubits, then we have to explore new ways to integrate other types of technology with our current setup.”

Funding: Equipment and experiments were supported by the Army Research Office and Physical Sciences Research Laboratory (ARO Grant No. W911NF2310077) and the Air Force Office of Scientific Research (AFOSR Grant No. FA9550-20-1-0270)