Dynamically Correcting a CNOT Gate for any Systematic Logical Error

TL;DR

This paper introduces composite pulse sequences that dynamically correct systematic errors in CNOT gates for any two-qubit interaction, improving fidelity in quantum computing systems with constant noise.

Contribution

The authors derive universal composite pulse sequences that correct systematic errors in CNOT gates for arbitrary two-qubit Hamiltonians, assuming error-free single-qubit gates.

Findings

Sequences correct errors to arbitrary order

Applicable to any two-qubit interaction Hamiltonian

Enhance fidelity in practical quantum systems

Abstract

We derive a set of composite pulse sequences that generates CNOT gates and correct all systematic errors within the logical subspace to arbitrary order. These sequences are applicable for any two-qubit interaction Hamiltonian, and make no assumptions about the underlying noise mechanism except that it is constant on the timescale of the operation. We do assume access to error-free single-qubit gates, so single-qubit gate imperfections eventually limit the achievable fidelity. However, since single-qubit gates generally have much higher fidelities than two-qubit gates in practice, these pulse sequences offer useful dynamical correction for a wide range of coupled qubit systems.