New nanowire qubits may lead to quantum computing
Semiconductor materials are the foundation of modern electronic devices. One thing that makes semiconductors so versatile is the ability to control the flow of charge using electric fields. Within the EU-funded project HYWIRE (Hybrid nanowire devices for quantum information processing) scientists used electric fields to effectively control superconducting qubit devices with Josephson junction elements made from semiconductor nanowires materials. Josephson junctions are typically made from aluminium (Al) superconducting wires and an Al oxide barrier. However, scientists replaced the Al/Al oxide junction with an InAs nanowire (weak link) coupling two semiconductors. To contact the nanowire, the team used superconducting Al contacts that were carefully grown by molecular beam epitaxy, allowing for pristine superconductor-semiconductor contacts. By applying carefully controlled voltages to the qubit gate electrodes, scientists could precisely manipulate the qubit states. Unlike conventional superconducting transmon qubits that are controlled using large on-chip currents, this gate-controlled transmon, or gatemon, uses low power dissipation voltages. As superconducting qubit devices typically operate at ultra low temperatures on the order of a millikelvin having qubits with low power control may simplify the challenge of scaling to larger architectures. Over the course of the project, the team tested two generations of devices. In the improved second generation of devices, scientists demonstrated that fragile quantum information could be maintained for up to 10 µs. The team also conducted experiments with a two-qubit gatemon circuit, thereby demonstrating the potential of gatemon qubits for building scalable quantum processors. In addition to developing this new type of qubit, the project team developed a set-up for picking up and precisely placing individual nanowires, thereby allowing controlled assembly of nanowire devices. Project results were published in peer reviewed journals and could lead to new advances in the field of quantum computing.
Keywords
Nanowire, quantum computing, qubits, spin-orbit interaction, HYWIRE, gatemon
