Demonstration of quantum error correction and universal gate set on a binomial bosonic logical qubit

TL;DR

This paper demonstrates full control of a single logical qubit encoded with a binomial bosonic code, including error correction and universal gate operations, achieving longer coherence and high fidelity, advancing fault-tolerant quantum computing.

Contribution

It experimentally achieves full control, error correction, and universal gates on a bosonic logical qubit, a significant step towards fault-tolerant quantum computation.

Findings

Logical qubit lifetime is 2.8 times longer with error correction.

Achieved 97.0% average process fidelity for logical gates.

First Ramsey experiment on a protected logical qubit with doubled coherence.

Abstract

Logical qubit encoding and quantum error correction (QEC) have been experimentally demonstrated in various physical systems with multiple physical qubits, however, logical operations are challenging due to the necessary nonlocal operations. Alternatively, logical qubits with bosonic-mode-encoding are of particular interest because their QEC protection is hardware efficient, but gate operations on QEC protected logical qubits remain elusive. Here, we experimentally demonstrate full control on a single logical qubit with a binomial bosonic code, including encoding, decoding, repetitive QEC, and high-fidelity (97.0% process fidelity on average) universal quantum gate set on the logical qubit. The protected logical qubit has shown 2.8 times longer lifetime than the uncorrected one. A Ramsey experiment on a protected logical qubit is demonstrated for the first time with two times longer coherence than the unprotected one. Our experiment represents an important step towards fault-tolerant quantum computation based on bosonic encoding.