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

摘要

We present an approach that allows quantifying decoherence processes in anopen quantum system subject to external time-dependent control. Interactionswith the environment are modeled by a standard bosonic heat bath. We developtwo unitarity-preserving approximation schemes to calculate the reduced densitymatrix. One of the approximations relies on a short-time factorization of theevolution operator, while the other utilizes expansion in terms of thesystem-bath coupling strength. Applications are reported for two illustrativesystems: an exactly solvable adiabatic model, and a model of a rotating-wavequantumcomputing gate function. The approximations are found to produceconsistent results at short and intermediate times.