Decoherence of coupled qubit system

TL;DR

This paper investigates how qubit systems decohere due to qubit flip processes, analyzing entropy evolution and the impact of noise, revealing quantum Brownian motion characteristics and importance of background charge fluctuations.

Contribution

It introduces a detailed analysis of decoherence in coupled qubits using influence functional, emphasizing the effects of qubit flips and noise on entropy and system dynamics.

Findings

Qubit flip processes cause oscillations and self-excitation.

Slower random telegraph noise results in more mixed states.

Background charge fluctuations significantly affect charge qubit decoherence.

Abstract

In this study, we examine decoherence of qubits system coupled independently by using influence functional. We especially concentrated on the effect of qubit flip process. We examine the zero-dimensional qubit and one-dimensional qubits system coupled with multi-band one-dimensional system. The qubit flip process leads to oscillation and self-excitation. We also obtained the time evolution of von Neumann entropy.The pure dephasing channel indicates entropy. These results show quantum brown motion. We present the numerical calculation of the entropy for random telegraph noise. This indicates that the slower random telegraph noise leads to more mixed state.Thus for charge qubit, the background charge fluctuation is important.