Universal Quantum Degeneracy Point for Superconducting Qubits

TL;DR

This paper introduces a universal quantum degeneracy point in superconducting qubits that protects against all types of low-frequency noise, enabling high-fidelity quantum logic gates and robustness to fabrication imperfections.

Contribution

It proposes a universal degeneracy point scheme that shields encoded qubits from arbitrary low-frequency noise in superconducting circuits.

Findings

Protection against both transverse and longitudinal low-frequency noise.

High-fidelity quantum logic gates on encoded qubits.

Robustness to fabrication parameter spreads.

Abstract

The quantum degeneracy point approach [D. Vion et al., Science 296, 886 (2002)] effectively protects superconducting qubits from low-frequency noise that couples with the qubits as transverse noise. However, low-frequency noise in superconducting qubits can originate from various mechanisms and can couple with the qubits either as transverse or as longitudinal noise. Here, we present a quantum circuit containing a universal quantum degeneracy point that protects an encoded qubit from arbitrary low-frequency noise. We further show that universal quantum logic gates can be performed on the encoded qubit with high gate fidelity. The proposed scheme is robust against small parameter spreads due to fabrication errors in the superconducting qubits.