Evaluation of Decoherence for Quantum Computing Architectures: Qubit System Subject to Time-Dependent Control

TL;DR

This paper introduces methods to quantify decoherence in open quantum systems with time-dependent control, using approximations that preserve unitarity, and applies them to models relevant for quantum computing.

Contribution

It develops two unitarity-preserving approximation schemes for calculating decoherence in quantum systems under external control, applicable to quantum computing architectures.

Findings

The approximations yield consistent results at short and intermediate times.

Application to models demonstrates the methods' effectiveness.

Provides tools for analyzing decoherence in quantum computing systems.

Abstract

We present an approach that allows quantifying decoherence processes in an open quantum system subject to external time-dependent control. Interactions with the environment are modeled by a standard bosonic heat bath. We develop two unitarity-preserving approximation schemes to calculate the reduced density matrix. One of the approximations relies on a short-time factorization of the evolution operator, while the other utilizes expansion in terms of the system-bath coupling strength. Applications are reported for two illustrative systems: an exactly solvable adiabatic model, and a model of a rotating-wave quantumcomputing gate function. The approximations are found to produce consistent results at short and intermediate times.