Ground-state characterization of Nb charge-phase Josephson qubits

Abstract

We present investigations of Josephson charge-phase qubits 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 60 nm and 80 nm are fabricated from Nb trilayer and allowing the determination of relevant sample parameters at liquid helium temperature. The observed partial suppression of the circulating supercurrent at 4.2 K is explained in 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 20 mK, demonstrating both the magnetic control of phase and the electrostatic control of charge on the qubit island.

8 pages, 8 figures

References in corpus (2)

• Reading-out the state inductively and microwave spectroscopy of an interferometer-type charge qubit
• Single-charge devices with ultrasmall Nb/AlOx/Nb trilayer Josephson junctions

Cited by in corpus (5)

• Majorana Fermions and a Topological Phase Transition in Semiconductor-Superconductor Heterostructures
• Quantum theory of the low-frequency linear susceptibility of interferometer-type superconducting qubits
• Current-Phase Relation and Josephson Inductance of Superconducting Cooper Pair Transistor
• Quasi-particle transitions in charge-phase qubits probed by rf oscillations
• The two Josephson junction flux qubit with large tunneling amplitude