The hybrid Josephson rhombus: A superconducting element with tailored current-phase relation

Abstract

Controlling the current-phase relation (CPR) of Josephson elements is essential for tailoring the eigenstates of superconducting qubits, tuning the properties of parametric amplifiers, and designing nonreciprocal superconducting devices. Here, we introduce the hybrid Josephson rhombus, a highly tunable superconducting circuit containing four semiconductor-superconductor hybrid Josephson junctions embedded in a loop. Combining magnetic frustration with gate-voltage-controlled tuning of individual Josephson couplings provides deterministic control of the harmonic content of the rhombus CPR. We show that for balanced Josephson couplings at full frustration, the hybrid rhombus displays a $\pi$-periodic $\cos (2\phi )$ potential, indicating coherent charge-$4e$ transport. Tuning away from the balanced configuration, we observe a superconducting diode effect with efficiency exceeding 25%. These results showcase the potential of hybrid Josephson rhombi as fundamental building blocks for noise-resilient qubits and quantum devices with custom transport properties.

12 pages, 7+3 figures

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Cited by in corpus (6)

• A Review of Design Concerns in Superconducting Quantum Circuits
• Superconducting Quantum Interference Devices based on InSb nanoflag Josephson junctions
• Gatemon Qubit Revisited for Improved Reliability and Stability
• Gate-tunable Josephson diodes in magic-angle twisted bilayer graphene
• Protected phase gate for the $0$-$\pi$ qubit using its internal modes
• Towards a $\cos (2\phi )$ Josephson element using aluminum junctions with well-transmitted channels