Protecting logical qubits with dynamical decoupling

TL;DR

This paper presents a novel dynamical decoupling scheme for logical qubits that significantly extends coherence times and demonstrates that logical qubits can outperform physical qubits in superconducting systems, advancing reliable quantum computing.

Contribution

The paper introduces a new dynamical decoupling scheme implementing iSWAP gates on logical qubits, demonstrating enhanced coherence and logical qubit performance in superconducting transmon qubits.

Findings

Logical qubits' coherence time extended by up to 366%.

Multiple logical qubits outperform physical qubits.

Universal logical gates successfully implemented.

Abstract

Demonstrating that logical qubits outperform their physical counterparts is a milestone for achieving reliable quantum computation. Here, we propose to protect logical qubits with a novel dynamical decoupling scheme that implements iSWAP gates on nearest-neighbor physical qubits, and experimentally demonstrate the scheme on superconducting transmon qubits. In our scheme, each logical qubit only requires two physical qubits. A universal set of quantum gates on the logical qubits can be achieved such that each logical gate comprises only one or two physical gates. Our experiments reveal that the coherence time of a logical qubit is extended by up to 366% when compared to the better-performing physical qubit. Moreover, to the best of our knowledge, we demonstrate for the first time that multiple logical qubits outperform their physical counterparts in superconducting qubits. We illustrate a set of universal gates through a logical Ramsey experiment and the creation of a logical Bell state. Given its scalable nature, our scheme holds promise as a component for future reliable quantum computation.