A universal quantum supercomputer proficient in beating today’s classical computers in solving many different problems remains the biggest ultimate prize for many engineers and researchers. Researchers from Google and the University of California Santa Barbara have taken an essential step towards the goal of developing a large-scale quantum computer.
Writing in the journal Quantum Science and Technology, they present a new method for producing superconducting interconnects, which are cooperative with existing superconducting qubit technology.
The race to develop the first large-scale error-corrected quantum computer is exceptionally competitive, and the process itself is complicated. Whereas traditional computers encode data into binary digits that exist in one of two states, a quantum computer reserves data in quantum bits that may be entangled with each other and placed in a superposition of both states simultaneously.
The discovery is that quantum states are amazingly fragile, and any undesired interaction with the surrounding environment may destroy this quantum information. One of the most significant hurdles in the creation of a large-scale quantum computer is how to scale up the number of qubits, while still combining command signals to them and preserving these quantum states.
Head author Brooks Foxen, from UC Santa Barbara, stated that there are a lot of unknowns when it comes to visualizing precisely what the first large-scale quantum computer will resemble like. In the superconducting qubit field, we are just now starting to examine systems with 10s of qubits whereas the long-term purpose is to build a computer with millions of qubits.
“Previous research has mostly involved layouts where control wires are routed on a single metal layer. More magnetic circuits require the capability to route wiring in three dimensions so that wires may cross over each other. Resolving this problem without introducing materials that overcome the feature of superconducting qubits is a hot topic, and several groups have recently displayed possible solutions. We accept that our solution, which is the first to give fully superconducting interconnects with significant high currents, offers the most flexibility in designing other aspects of quantum circuits.
As superconducting qubit technology grows beyond one-dimensional chains of nearest neighbour joined qubits, larger-scale two-dimensional arrays are a natural next step.
Prototypical two-dimensional arrays have been made, but the difficulty of routing control wiring and readout circuitry has, so far, limited the development of high accuracy qubit arrays of size 3×3 or more critical.
Senior author Professor John M Martinis, collectively appointed at both Google and UC Santa Barbara, continued that to allow the development of larger qubit arrays, we have emerged a process for fabricating fully superconducting interconnects that are substantially compatible with our existing, high accuracy, aluminium on silicon qubits. This fabrication method opens the door to the possibility of the close combination of two superconducting circuits with each other or, as would be desirable in the case of superconducting qubits, the tight integration of one high-coherence qubit device with a compact, multi-layer, signal-routing device.