Scientists at Brookhaven National Laboratory have developed a new qubit architecture that could make it easier to manufacture quantum computers. The new design uses constriction junctions instead of the traditional sandwich-like “SIS” junctions. SIS junctions have two superconducting layers (Al) separated by an insulator (AlOX).
They are known for their coherence, which is how long qubits maintain quantum information. However, they are challenging to make precisely at a large scale. Constriction junctions have two superconducting layers connected by a thin superconducting wire.
They lay flat and can be made more easily in large numbers. The study showed that qubits with constriction junctions perform just as well as qubits with SIS junctions.
New qubit architecture for easier production
The research was done as part of the Co-design Center for Quantum Advantage (C2QA), a DOE National Quantum Information Science Research Center led by Brookhaven Lab. The scientists did mathematical analyses to create a guide for making qubits more easily and reliably. One challenge was that constriction junctions initially allow more current than SIS junctions.
The researchers found that using less common superconducting metals could reduce the current to the right levels for qubits. They also discovered that they could tune the nonlinearity of constriction junctions by choosing specific superconducting materials and adjusting the junction’s size and shape. Nonlinearity is important for qubits to operate between just two energy levels.
The scientists are now exploring materials that meet the strict requirements they identified. They are particularly interested in superconducting transition metal silicides, which are already used in making semiconductors. The study, published in Physical Review A, aligns with C2QA’s goal of developing a qubit architecture that works well for quantum computing and can be integrated with existing electronics manufacturing.
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