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Frontiers of Physics

All-optical entanglement recovery in a correlated noisy channel

Qiqi Zhu, Yujia Fan, Shengzhi Xiao, Yanbo Lou, Shengshuai Liu, Jietai Jing

Published Nov 20, 2025• 1 citation
Publisher

Abstract

The task of protecting quantum entanglement is crucial for quantum communication. Conventionally, correlated noise correction requires an electro-optic modulation process, which limits the application of such correction schemes in constructing broadband quantum communication. Here, we experimentally demonstrate a scheme of all-optical entanglement recovery in a correlated noisy channel without electro-optic modulation. In our scheme, the correlated noisy channel is enabled by an Einstein−Podolsky−Rosen entangled state, a low-noise parametric amplifier, and a beam splitter, thereby avoiding electro-optic conversion. Quantum entanglement is destroyed after one half of the quantum entangled state passes through the noisy channel. Such quantum entanglement can be recovered in the auxiliary noisy channel which shares correlated noise with the noisy channel. Our results pave the way for deterministically implementing all-optical quantum secure communication.

DOI
10.15302/frontphys.2026.062201

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A quantum communication network can be constructed by distributing a multipartite entangled state to space-separated nodes. Entangled optical beams with highest flying speed and measurable brightness can be used as carriers to convey information in quantum communication networks. Losses and noises existing in real communication channels will reduce or even totally destroy entanglement. The phenomenon of disentanglement will result in the complete failure of quantum communication. Here, we present the experimental demonstrations on the disentanglement and the entanglement revival of tripartite entangled optical beams used in a quantum network. We experimentally demonstrate that symmetric tripartite entangled optical beams are robust in pure lossy but noiseless channels. In a noisy channel, the excess noise will lead to the disentanglement and the destroyed entanglement can be revived by the use of a correlated noisy channel (non-Markovian environment). The presented results provide useful technical references for establishing quantum networks.
Amplification of an entangled state is a matter of great significance in quantum communication. However, any parametric amplifier (PA) will introduce added noise into the system which unavoidably degrades the entanglement or even makes it disappear. Recently, it has been experimentally demonstrated that amplification of one half of a two-mode squeezed state is possible while preserving entanglement [Phys. Rev. Lett. 103, 010501 (2009)]. However, such entanglement cannot be maintained when the strength of the amplification is large. To solve this problem, we propose a correlation modulation scheme (CMS), which fully exploits the quantum correlation between the two output states from the PA process, to suppress the added noise from the parametric amplifications. For amplifying an entangled state using a PA, we demonstrate that the CMS not only better maintains but also always preserves the entanglement whatever the strength of the PA. Such a CMS may pave the way to low-noise amplification of an entangled state.
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