Quasi-Classical Rules for Qubit Spin-Rotation Error Suppression

TL;DR

This paper demonstrates that composite pulse sequences for suppressing qubit spin-rotation errors can be derived using a quasi-classical approach, questioning whether entanglement-based error correction offers unique advantages.

Contribution

It shows that error-suppressing pulse sequences can be understood within a quasi-classical framework, challenging the necessity of entanglement in certain quantum error correction methods.

Findings

Composite pulses can be derived from a quasi-classical perspective.

The geometric interpretation of error suppression is preserved in the quasi-classical approach.

Entanglement-based error correction may not be fundamentally necessary for certain pulse sequences.

Abstract

A frequently encountered source of systematic error in quantum computations is imperfections in the control pulses which are the classical fields that control qubit gate operations. From an analysis of the quantum mechanical time-evolution operator of the spin wavefunction, it has been demonstrated that composite pulses can mitigate certain systematic errors and an appealing geometric interpretation was developed for the design of error-suppressing composite pulses. Here we show that these same pulse sequences can be obtained within a quasi-classical framework. This raises the question of whether error-correction procedures exist that exploit entanglement in a manner that can not be reproduced in the quasi-classical formulation.