Quasi-Hamiltonian Method for Computation of Decoherence Rates

TL;DR

This paper introduces a new mathematical method to analyze broad-spectrum noise in quantum computing qubits, enabling extraction of noise characteristics and predicting a novel noise-induced looping effect on the Bloch sphere.

Contribution

The paper presents a quasi-Hamiltonian approach applicable across all qubit working points, facilitating noise parameter extraction and revealing a new physical effect of noise-induced looping.

Findings

Superconducting qubits are near the regime for observing noise-induced looping.

The method allows for characterization of 1/f noise from qubit measurements.

Predicted looping effect could impact qubit coherence understanding.

Abstract

For many implementations of quantum computing, 1/f and other types of broad-spectrum noise are an important source of decoherence. An important step forward would be the ability to back out the characteristics of this noise from qubit measurements and to see if it leads to new physical effects. For certain types of qubits, the working point of the qubit can be varied. Using a new mathematical method that is suited to treat all working points, we present theoretical results that show how this degree of freedom can be used to extract noise parameters and to predict a new effect: noise-induced looping on the Bloch sphere. We analyze data on superconducting qubits to show that they are very near the parameter regime where this looping should be observed.