Superconducting pi qubit with three Josephson junctions

TL;DR

This paper introduces a novel superconducting pi qubit design using a ring with two zero and one pi Josephson junctions, enabling stable quantum states with minimal external magnetic field influence.

Contribution

It proposes a new superconducting qubit architecture utilizing ferromagnetic pi junctions, enhancing scalability and noise robustness compared to existing designs.

Findings

Degenerate stable states emerge without external magnetic field.

Quantum tunneling creates coherent bonding and antibonding states.

The design allows for small external magnetic field manipulation.

Abstract

We propose a new qubit consisting of a superconducting ring with two ordinary zero junctions and one ferromagnetic pi junction. In the system, two degenerate stable states appear in the phase space without an external magnetic field because of a competition between the zero and pi states. Quantum tunneling between the two degenerate states leads to a formation of bonding and antibonding states (coherent states) which are used as a bit. For manipulating the states of the qubit, only small external magnetic field around zero is required. This feature leads to a large-scale integration and a construction of the qubit with a smaller size which is robust to the decoherence by external noises.