Autonomous error correction of a single logical qubit using two transmons

TL;DR

This paper demonstrates a hardware-efficient autonomous quantum error correction scheme using only two transmons, actively correcting photon loss and passively reducing dephasing, thereby improving qubit state fidelity.

Contribution

The work introduces a novel AQEC method with minimal qubits, utilizing steady-state bath engineering for effective error correction in a scalable architecture.

Findings

Achieved factors of 2.0, 5.1, and 1.4 improvements for logical states

Implemented with only two transmon qubits in a 2D architecture

Effectively corrects photon loss and suppresses dephasing

Abstract

Large-scale quantum computers will inevitably need quantum error correction to protect information against decoherence. Traditional error correction typically requires many qubits, along with high-efficiency error syndrome measurement and real-time feedback. Autonomous quantum error correction (AQEC) instead uses steady-state bath engineering to perform the correction in a hardware-efficient manner. We realize an AQEC scheme, implemented with only two transmon qubits in a 2D scalable architecture, that actively corrects single-photon loss and passively suppresses low-frequency dephasing using six microwave drives. Compared to uncorrected encoding, factors of 2.0, 5.1, and 1.4 improvements are experimentally witnessed for the logical zero, one, and superposition states. Our results show the potential of implementing hardware-efficient AQEC to enhance the reliability of a transmon-based quantum information processor.