The leading technology for quantum computers is based on superconducting qubits called transmons. Ease of fabrication has been a key advantage of transmons over their main superconducting competitors, fluxonium qubits, which consist of loops of many nanoscale Josephson junctions. Recent advances in nanofabrication have made fluxonium qubits easier to engineer, however, triggering a new wave of interest in this architecture (see Viewpoint: Fluxonium Steps up to the Plate). Now University of Chicago physicists Helin Zhang and Chunyang Ding and their collaborators have realized a tunable interaction between two fluxonium qubits, which allowed them to demonstrate a two-qubit gate with a fidelity (a reliability metric for a quantum device) exceeding 99.9% [1]. The result is an important step toward building large-scale fluxonium-based quantum computers, the researchers say.
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