Exact Master Equation and Non-Markovian Decoherence for Quantum Dot Quantum Computing

TL;DR

This paper presents an exact master equation approach to analyze non-Markovian decoherence in quantum dot quantum computing systems, including charge qubits and measurement-induced effects, providing detailed insights into environmental interactions.

Contribution

It derives a general exact master equation applicable to complex nanostructures and applies it to study decoherence in double quantum dot charge qubits under various conditions.

Findings

Decoherence dynamics are predominantly non-Markovian.

Quantum point contact measurement induces significant decoherence.

The exact master equation captures complex environmental interactions.

Abstract

In this article, we report the recent progress on decoherence dynamics of electrons in quantum dot quantum computing systems using the exact master equation we derived recently based on the Feynman-Vernon influence functional approach. The exact master equation is valid for general nanostructure systems coupled to multi-reservoirs with arbitrary spectral densities, temperatures and biases. We take the double quantum dot charge qubit system as a specific example, and discuss in details the decoherence dynamics of the charge qubit under coherence controls. The decoherence dynamics risen from the entanglement between the system and the environment is mainly non-Markovian. We further discuss the decoherence of the double-dot charge qubit induced by quantum point contact (QPC) measurement where the master equation is re-derived using the Keldysh non-equilibrium Green function technique due to the non-linear coupling between the charge qubit and the QPC. The non-Markovian decoherence dynamics in the measurement processes is extensively discussed as well.