Superconducting-silicon qubits

Using a bottom-up approach to make hybrid quantum devices

Theorists propose a way to make superconducting quantum devices such as Josephson junctions and qubits, atom-by-atom, inside a silicon crystal. Such systems could combine the most promising aspects of silicon spin qubits with the flexibility of superconducting circuits. The researcher’s results have now been published in Nature Communications.

High quality silicon is one of the historical foundations of modern computing. But it is also promising for quantum information technology. In particular, electron and nuclear spins in pure silicon crystals have been measured to have excellent properties as long-lived qubits, the equivalent of bits in conventional computers.

In a paper appearing this week in Nature Communications, Yun-Pil Shim and Charles Tahan from the University of Maryland and the Laboratory for Physical Sciences (on the College Park, MD campus) have shown how superconducting qubits and devices can be constructed out of silicon. Doing so can potentially combine the good quantum properties of silicon and the ubiquity of semiconductor technology with the flexibility of superconducting devices. They propose using “bottom-up” nano-fabrication techniques to construct precisely placed superconducting regions within silicon or germanium and show that such “wires” can be used to make superconducting tunnel junctions and other useful superconducting devices.

Beyond the possibility of superconducting circuits built inside a homogeneous silicon crystal, engineered superconducting-semiconductor devices like these could be used to build other types of exotic quantum many-body systems, at the atomic scale, and even act as testbeds for our understanding of superconductivity itself.

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