Ground-state characterization of Nb charge-phase Josephson qubits

H. Zangerle; J. Könemann; B. Mackrodt; R. Dolata; S. V. Lotkhov; S. A. Bogoslovsky; M. Götz; A. B. Zorin

doi:10.1103/PhysRevB.73.224527

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Ground-state characterization of Nb charge-phase Josephson qubits

H. Zangerle, J. Könemann, B. Mackrodt, R. Dolata, S. V. Lotkhov, S. A. Bogoslovsky, M. Götz, A. B. Zorin

DOI 10.1103/PhysRevB.73.224527 · Physical Review B

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Abstract

We present investigations of Josephson charge-phase qubits of superconducting quantum interference device (SQUID) configuration, inductively coupled to a radio-frequency-driven tank circuit, enabling the readout of the states by measuring the Josephson inductance of the qubit. The circuits, including junctions with linear dimensions of 60nm×60nm and 80nm×80nm, are fabricated from Nb∕AlOx∕Nb trilayer and allow the determination of relevant sample parameters at liquid helium temperature. The observed partial suppression of the circulating supercurrent in the qubit loop at 4.2K is explained within the framework of a quantum-statistical model. We have probed the ground-state properties of qubit structures with different ratios of the Josephson coupling to Coulomb charging energy at 20mK, demonstrating both the magnetic control of phase and the electrostatic control of charge of the qubit.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown