Protecting quantum entanglement between error-corrected logical qubits

• URL: http://arxiv.org/abs/2302.13027v1
• Date: Sat, 25 Feb 2023 08:57:28 GMT
• Title: Protecting quantum entanglement between error-corrected logical qubits
• Authors: Weizhou Cai, Xianghao Mu, Weiting Wang, Jie Zhou, Yuwei Ma, Xiaoxuan Pan, Ziyue Hua, Xinyu Liu, Guangming Xue, Haifeng Yu, Haiyan Wang, Yipu Song, Chang-Ling Zou, and Luyan Sun
• Abstract summary: We experimentally realize entangled logical qubits (ELQ) with a bosonic quantum module by encoding quantum information into spatially separated microwave modes. The coherence time of the purified ELQ via error detection is improved by 45$%$ compared with the unprotected ELQ. In addition, violation of the Bell inequality by logical qubits is demonstrated for the first time with the measured Bell signal B=2.250$pm$0.019 after purification.
• Score: 21.656211734079996
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Entanglement represents one of the most important conceptual advances in physics during the last century and is also one of the most essential resources in quantum information science. However, entanglement is fragile and its potential advantages in applications are hindered by decoherence in practice. Here, we experimentally realize entangled logical qubits (ELQ) with a bosonic quantum module by encoding quantum information into spatially separated microwave modes. The entanglement is protected by repetitive quantum error correction, and the coherence time of the purified ELQ via error detection is improved by 45$\%$ compared with the unprotected ELQ and exceeds that of the entangled physical qubits. In addition, violation of the Bell inequality by logical qubits is demonstrated for the first time with the measured Bell signal B=2.250$\pm$0.019 after purification, surpassing the classical bound by 13 standard deviations. The protected ELQ could be applied in future explorations of quantum foundations and applications of quantum networks.

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