Decoherence in adiabatic quantum computation

TL;DR

This paper investigates how decoherence affects adiabatic quantum computation, revealing that global AQC is robust against certain noise types, while local AQC's efficiency diminishes with decoherence, emphasizing the importance of phase coherence.

Contribution

It provides a detailed analysis of decoherence effects on AQC, especially under non-Markovian noise, and compares the robustness of global versus local AQC strategies.

Findings

Global AQC maintains properties despite decoherence larger than the minimum gap.

Local AQC does not improve scaling under decoherence, unlike in ideal conditions.

Phase coherence is essential for scaling improvements in AQC.

Abstract

We have studied the decoherence properties of adiabatic quantum computation (AQC) in the presence of in general non-Markovian, e.g., low-frequency, noise. The developed description of the incoherent Landau-Zener transitions shows that the global AQC maintains its properties even for decoherence larger than the minimum gap at the anticrossing of the two lowest energy levels. The more efficient local AQC, however, does not improve scaling of the computation time with the number of qubits $n$ as in the decoherence-free case. The scaling improvement requires phase coherence throughout the computation, limiting the computation time and the problem size n.