Engineering Superconducting Phase Qubits

TL;DR

This paper explores the use of $\

Contribution

It introduces a novel design of superconducting phase qubits utilizing $\

Findings

Demonstrates construction of degenerate two-level junctions.

Shows how to engineer superconducting phase switches.

Proposes qubits that operate without external biasing.

Abstract

The superconducting phase qubit combines Josephson junctions into superconducting loops and defines one of the promising solid state device implementations for quantum computing. While conventional designs are based on magnetically frustrated superconducting loops, here we discuss the advantages offered by $\pi$-junctions in obtaining naturally degenerate two-level systems. Starting from a basic five-junction loop, we show how to construct degenerate two-level junctions and superconducting phase switches. These elements are then effectively engineered into a superconducting phase qubit which operates exclusively with switches, thus avoiding permanent contact with the environment through external biasing. The resulting superconducting phase qubits can be understood as the macroscopic analogue of the `quiet' s-wave-d-wave-s-wave Josephson junction qubits introduced by Ioffe {\it et al.} [Nature {\bf 398}, 679 (1999)].