Quantum pathology of static internal imperfections in flawed quantum computers

TL;DR

This paper investigates how residual internal imperfections, especially two-body flaws, impact the performance of quantum gates in isolated quantum computers, highlighting the significance of coherent shifts over decoherence.

Contribution

It reveals that strong two-body imperfections can improve gate performance and identifies coherent shifts as the main error source, emphasizing internal flaws in quantum computer design.

Findings

Performance improves with stronger two-body imperfections

Coherent shifts are the primary source of error

Internal flaws significantly affect quantum gate fidelity

Abstract

Even in the absence of external influences the operability of a quantum computer (QC) is not guaranteed because of the effects of residual one- and two-body imperfections. Here we investigate how these internal flaws affect the performance of a quantum controlled-NOT (CNOT) gate in an isolated flawed QC. First we find that the performance of the CNOT gate is considerably better when the two-body imperfections are strong. Secondly, we find that the largest source of error is due to a coherent shift rather than decoherence or dissipation. Our results suggest that the problem of internal imperfections should be given much more attention in designing scalable QC architectures.