Fabrication and measurements of hybrid Nb/Al Josephson junctions and flux qubits with pi-shifters

Abstract

We describe fabrication and testing of composite flux qubits combining Nb- and Al-based superconducting circuit technology. This hybrid approach to making qubits allows for employing pi-phase shifters fabricated using well-established Nb-based technology of superconductor-ferromagnet-superconductor Josephson junctions. The important feature here is to obtain high interface transparency between Nb and Al layers without degrading sub-micron shadow mask. We achieve this by in-situ Ar etching using e-beam gun. Shadow-evaporated Al/AlOx/Al Josephson junctions with Nb bias pads show the expected current-voltage characteristics with reproducible critical currents. Using this technique, we fabricated composite Nb/Al flux qubits with Nb/CuNi/Nb pi-shifters and measured their magnetic field response. The observed offset between the field responses of the qubits with and without pi-junction is attributed to the pi phase shift. The reported approach can be used for implementing a variety of hybrid Nb/Al superconducting quantum circuits.

arXiv comment9 pages, 5 figures

References in corpus (12)

• Circuit Quantum Electrodynamics: Coherent Coupling of a Single Photon to a Cooper Pair Box
• Cavity quantum electrodynamics for superconducting electrical circuits: an architecture for quantum computation
• Atomic physics and quantum optics using superconducting circuits
• Coherent Quantum Dynamics of a Superconducting Flux Qubit
• Quiet SDS Josephson Junctions for Quantum Computing
• Implementation of superconductor-ferromagnet-superconductor pi-shifters in superconducting digital and quantum circuits
• Temperature dependence of coherent oscillations in Josephson phase qubits
• One- and two-photon spectroscopy of a flux qubit coupled to a microscopic defect
• Imaging spontaneous currents in superconducting arrays of pi-junctions
• Quantum dynamics in a camel-back potential of a dc SQUID
• Spectroscopy of a Qubit Array via a Single Transmission Line
• Nonlinear resonant behavior of the dispersive readout scheme for a superconducting flux qubit

Cited by in corpus (17)

• Loss mechanisms in superconducting thin film microwave resonators
• Ferromagnetic Materials for Josephson π Junctions
• Electrodynamics of highly spin-polarized tunnel Josephson junctions
• Superconducting flux qubit with ferromagnetic Josephson $\pi$-junction operating at zero magnetic field
• Superconducting circuit simulator of Bose-Hubbard model with a flat band
• Thermal conductance of Nb thin films at sub-kelvin temperatures
• Oscillatory superconducting transition temperature in superconductor/antiferromagnet heterostructures
• Controllable supercurrent in mesoscopic superconductor-normal metal-ferromagnet crosslike Josephson structures
• Gate-tunable nonlocal Josephson effect through magnetic van der Waals bilayers
• Shortcuts to adiabaticity in superconducting circuits for fast multi-partite state generation
• Supercurrent-induced long-range triplet correlations and controllable Josephson effect in superconductor/ferromagnet hybrids with extrinsic SOC
• The superconducting circuit companion -- an introduction with worked examples
• Neel proximity effect in superconductor/antiferromagnet heterostructures
• Voltage-driven dynamics of ${\phi }_0$-S/F/S Josephson junctions chains
• Evidence of the inverse proximity effect in tunnel magnetic Josephson Junctions
• Anomalous phase shift and superconducting diode effect in Josephson junctions via thin films of rare-earth intermetallic magnets
• Large critical current density Josephson $\pi$ junctions with PdNi barriers