Decoherence in quantum walks and quantum computers

TL;DR

This paper investigates how decoherence affects quantum walks and quantum computers by modeling system-environment interactions through toy models, highlighting challenges in maintaining quantum coherence in realistic scenarios.

Contribution

It introduces and analyzes three toy models of decoherence in quantum walks, providing insights into their impact on quantum information processing.

Findings

Decoherence significantly disrupts quantum walks in the models studied.

Different environmental couplings have distinct effects on quantum coherence.

Results suggest challenges for scalable quantum computing under realistic decoherence conditions.

Abstract

Decoherence is the major stumbling block in the realization of a large-scale quantum computer. Ingenious methods have been devised to overcome decoherence, but their success has been proven only for over-simplified models of system-environment interaction. Whether such methods will be reliable in the face of more realistic models is a fundamental open question. In this partly pedagogical article, we study two toy models of quantum information processing, using the language of \emph{quantum walks}. Decoherence is incorporated in 3 ways - by coupling to a noisy `projective measurement' system, and by coupling to oscillator and spin baths.