Manifold algorithmic errors in quantum computers with static internal imperfections

TL;DR

This paper investigates how static internal imperfections in quantum computers cause errors, revealing that certain errors are difficult to correct retroactively and emphasizing the need for concurrent error correction during gate operations.

Contribution

It provides a detailed numerical analysis of errors caused by static imperfections in Josephson charge qubits, highlighting their impact on quantum gate fidelity and error correction strategies.

Findings

Errors behave like a perturbed kicked top with weak fidelity decay dependence

Retroactive error correction may be ineffective for static imperfections

Effective error correction must be integrated during gate implementation

Abstract

The inevitable existence of static internal imperfections and residual interactions in some quantum computer architectures result in internal decoherence, dissipation, and destructive unitary shifts of active algorithms. By exact numerical simulations we determine the relative importance and origin of these errors for a Josephson charge qubit quantum computer. In particular we determine that the dynamics of a CNOT gate interacting with its idle neighboring qubits via native residual coupling behaves much like a perturbed kicked top in the exponential decay regime, where fidelity decay is only weakly dependent on perturbation strength. This means that retroactive removal of gate errors (whether unitary or non-unitary) may not be possible, and that effective error correction schemes must operate concurrently with the implementation of subcomponents of the gate.