Time evolution of spin-boson system for different effective spectral density functions

TL;DR

This paper explores how different spectral density functions affect the dynamics of open qubits in spin-boson systems, revealing that coupling to a common bath can prolong decoherence and relaxation times, using a numerically exact method.

Contribution

It introduces two types of effective spectral density functions and analyzes their impact on qubit dynamics with a novel numerical approach.

Findings

Different spectral densities lead to distinct qubit dynamics.

Coupling to a common bath extends decoherence and relaxation times.

The iterative tensor multiplication algorithm effectively solves the system dynamics.

Abstract

In this paper we firstly obtain two kinds of effective spectral density functions by setting the cut-off frequencies of baths be infinite and finite. Secondly, we investigate the reduced dynamics of open qubits in four kinds of systems constructed with the basic spin-boson model. It is shown that the qubit has different dynamics governed by the two kinds of spectral density functions. In addition, we obtained that a qubit coupled to an intermediate harmonic oscillator has longer decoherence and relaxation times as they are coupled to a common bath than to their respective baths. In solving the dynamics of qubits we use a numerically exact algorithm, iterative tensor multiplication algorithm based on the quasiadiabatic propagator path integral scheme.