The tunable 0-\texorpdfstring{$\pi$}{Lg} qubit: Dynamics and Relaxation

TL;DR

This paper analyzes the dynamics and relaxation of a tunable 0-π qubit under time-dependent flux, exploring its coherence, transition probabilities, and potential for prolonged lifetime using quantum Zeno effects.

Contribution

It provides a systematic, gauge-invariant Hamiltonian treatment of the 0-π qubit with flux noise and demonstrates its coherent oscillations under sinusoidal drives, highlighting its tunability and potential for enhanced coherence.

Findings

Coherent oscillations observed near resonant frequencies.

Parameters can be tuned to prepare the system in its ground state.

Prolonged lifetime potential via weak measurement and quantum Zeno effect.

Abstract

We present a systematic treatment of a 0-\texorpdfstring{$\pi$}{Lg} qubit in the presence of a time-dependent external flux. A gauge-invariant Lagrangian and the corresponding Hamiltonian is obtained. The effect of the flux noise on the qubit relaxation is obtained using perturbation theory. Under a time-dependent drive of sinusoidal form, the survival probability, and transition probabilities have been studied for different strengths and frequencies. The driven qubit is shown to possess coherent oscillations among two distinct states for a weak to moderate strength close to resonant frequencies of the unperturbed qubit. The parameters can be chosen to prepare the system in its ground state. This feature paves the way to prolong the lifetime by combining ideas from weak measurement and quantum Zeno effect. We believe that this is an important variation of a topologically protected qubit which is tunable.