Josephson charge-phase qubit with radio frequency readout: coupling and decoherence

TL;DR

This paper investigates a charge-phase Josephson qubit with RF readout, analyzing coupling mechanisms and decoherence sources, and provides operational recommendations to minimize decoherence for improved quantum computing performance.

Contribution

It introduces a specific qubit design with RF readout and evaluates decoherence effects, offering strategies for optimal operation at magic points.

Findings

Decoherence due to control lines and measurement system quantified.

Operational points with minimal decoherence identified.

Coupling to RF tank circuit enables effective qubit state readout.

Abstract

The charge-phase Josephson qubit based on a superconducting single charge transistor inserted in a low-inductance superconducting loop is considered. The loop is inductively coupled to a radio-frequency driven tank circuit enabling the readout of the qubit states by measuring the effective Josephson inductance of the transistor. The effect of qubit dephasing and relaxation due to electric and magnetic control lines as well as the measuring system is evaluated. Recommendations for operation of the qubit in magic points producing minimum decoherence are given.