Demonstration of fidelity improvement using dynamical decoupling with superconducting qubits

TL;DR

This paper demonstrates that dynamical decoupling significantly improves the fidelity of superconducting qubits on IBM and Rigetti platforms, effectively mitigating dephasing and spontaneous emission errors without post-selection.

Contribution

It provides the first unconditional fidelity improvements using dynamical decoupling on real superconducting qubits in cloud-based quantum computers.

Findings

Fidelity gains achieved with dynamical decoupling over unprotected qubits.

Protection of entangled two-qubit states is possible, but to a lesser extent.

Dephasing and spontaneous emission are the main error sources mitigated by DD.

Abstract

Quantum computers must be able to function in the presence of decoherence. The simplest strategy for decoherence reduction is dynamical decoupling (DD), which requires no encoding overhead and works by converting quantum gates into decoupling pulses. Here, using the IBM and Rigetti platforms, we demonstrate that the DD method is suitable for implementation in today's relatively noisy and small-scale cloud based quantum computers. Using DD, we achieve substantial fidelity gains relative to unprotected, free evolution of individual superconducting transmon qubits. To a lesser degree, DD is also capable of protecting entangled two-qubit states. We show that dephasing and spontaneous emission errors are dominant in these systems, and that different DD sequences are capable of mitigating both effects. Unlike previous work demonstrating the use of quantum error correcting codes on the same platforms, we make no use of post-selection and hence report unconditional fidelity improvements against natural decoherence.